Weekends to birthday

123 days are 17 weeks plus 4 days and 119 days are exactly 17 weeks. In 119 days we will have lived 17 sundays. If today is Friday in 119 days we will be Friday. Adding the four days that last we will live another Sunday. So the answer is $\boxed{18}$ days

Say today is Day 0. Then Calvin's birthday is Day 123. We find the number of days Day $n$ such that $n\equiv 2\pmod 7$ . These are days $2,9,16\cdots,121$ . This is $\dfrac{121-2}{7}+1=\boxed{18}$ days.

First, we find how many complete weeks passed since Calvin's birthday. We can do this by simply finding $\lfloor \frac{123}{7} \rfloor$ , which equals to $17$ . So, after $17 \cdot 7=119$ days, 17 Sundays have passed. However, there are still 4 days remaining. Sunday is one of the 4 days after Friday, so there are $17+1=\boxed{18}$ Sundays between "today" and Calvin's birthday.

123 days = 17 weeks and 4 days. Total number of Sundays = 17+1 =18

A Sunday occurs every 7 days. For any multiple of 7 days we can divide it by 7 to find the number of Sundays.

If we subtract 4 days from 123 we get 119, which is a multiple of 7.

$\frac{119}{7}=17$

Okay, so in the next 119 days we get 17 Sundays. But we still have four days. Since it will be a Friday, ket's count four more days to see if we get another Sunday. Saturday, Sunday, Monday, Tuesday.

We did get another Sunday! So now we have $\boxed{18}$ Sundays in all. Happy Tuesday birthday, Calvin!

Here Friday is day "0" and then find number of days for the end of that week.(it is 2).[during these 2 days we find a sunday] .Substract that 2 from 123 gives 121 .Then the closest number divisible by 7 which is <= to 123 is 119. Therefore (121 - 2)/7 .This equals to 119/7 = 17.This means for Calvin's birthday there are 17 weeks each week has one a sunday. So there are 17 Sunday's for 119 days. At the start we found another sunday when completing the week. So after adding that too we get final answer as 17 + 1 =18. THEREFORE THERE ARE 18 SUNDAYS FOR CALVIN'S BIRTHDAY

There are 7 days in a week. Each week has one Sunday, so 123=7×17+4 Plus the Sunday after the Friday Therefore 17+1=18

1st Sunday is in 2 days

( 123 - 2 ) / 7 = 121 / 7 = 17,28...

x = 17 + 1 = 18

1 week=7 days Every week has a Sunday. So, 123/7=18 weeks.

divide 123 by 7

then we get 123 / 7 = 17 weeks and remainder 4 days. hence within 4 days there will be also a sunday and in 17 weeks there are 17 sundays .

hance,

Total sundays = 18

friday=> in 123 days to birthday, 123 days divide by 7(7 days in a week), 123/7 = 17 remainder 4.. meaning there's 4 days more to his birthday.. so.. it's friday now and +2 it will be another sunday. hence, u will get the answer 18... correct me if I am wrong

123/7=17.5 nearly equal to 18

Today is friday. Calvin birthday is in 123 days. So, in one week there is just one sunday and one week have 7 days. 123/7 = 17 remain 4. There is 17 days of sunday and +1 because today is friday and there is 4 more so one of them is sunday too. The answer is 18.

let start tha ans.-- in a week there are 7 days so,divide 123 by 7. ans is 17.5 but we know that sunday come after 3 days of friday. there r 17 friday come but what about 0.5. so,0.5*7=3.5 then friday + 3days = sunday so, ans is 17+1=18

123/7=18

divide 123 by 7 to know what day of the week calvin's birthday is. friday, plus 7 days, is the next friday. if the answer does not have a remainder, you have nothing to worry about. since 123 days divided by 7 days is 17 weeks and 4 days, calvin's birthday is on a tuesday. you have to do this in case you have an extra sunday which in this case, you do. so there are 17 sundays following the friday, plus the four days which includes another sunday.

123/7 = 17 and remaining 4. Hence 18 Sundays are there between that day and Calvin's birthday.

after 2 days 1 sunday. now day reamins are 121 and sunday occur in every 7 day so divide 121 by 7 u get 17.243 so take the whole no. +one sunday that is after friday so 18 sunday

123 (days until his birthday)/ 7 (days in a week)=~17.5 weeks that pass

we know at least 17 Sundays will pass.

For the remaining .5 it is safe to assume that there will be one more Sunday a half a week after Friday

Thus, 18 Sundays pass between Friday and Calvins next birthday

123/7=17sundays and 4days friday sat and another sunday so 17+1=18

Divide 123 by 7 and then round up because today is Friday

123/7 = 17.57 (round-off) = 18

count 123 days in calendar starting from friday :bd

Today is Friday, remaining days for Calvin's birthday is $123$

$2$ days after is Sunday, remaining days for Calvin's birthday is $123-2=121$

Hence, number of Sundays between is...

$\large{⌊\frac{121}{7}⌋} + 1 = \large{\fbox{18}}$