Todays problem

The given two equations are : Eq 1 : x + y = 20 Eq 2 : x - y = 0

Solution : Finding the value of x x + y = 20 x = 20 - y , which is Eq 3

Substituting the value of x in Eq 2 x - y = 0 20 - y - y = 0 , by eq 3 20 - 2y = 0 20 = 2y 20/2 = y 10 = y , or y = 10

Finding the value of x, by eq 3 x = 20 - y = 20 - 10 x = 10 y = 10

The correct answer is option A.

$x + y = 20$

$x - y = 0$

$2x = 20$

$x = 10$

$10 + y = 20$

$y = 20 - 10 = 10$

$\fbox{x = 10, y = 10}$

Since, x-y = 0, we know that x and y are equal. Thus, 20/2 = x and y. Therefore x = 10 and y = 10.

$x=\dfrac 12 \left ((x+y)+(x-y)\right ) =\dfrac 12 (20+0)=10$

$y=\dfrac 12 \left ((x+y)-(x-y) \right ) =\dfrac 12 (20-0)=10$

Therefore $\boxed {x=10,y=10}$ .

Given that $x-y=0$ , then $x=y$ .

We can use this in the first equation and we can see that $y+y=20 \Rightarrow 2y=20 \Rightarrow y=\boxed{10}$ and since $x=y$ we can conclude that $x=\boxed{10}$ too!