Age problem

In my math class, my teacher give me this problem:

"Three years ago, Nora was half as old as Mary is now. If Mary is four years older than Nora, how old is Mary now?"

The teacher did explained it to me but I have not clue what's going on. Please help me.

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Comments

Ok, so let's start off with some variables. Let's call Nora's age n and Mary's age m (right now we don't what they are). The first clue says that if you subtract n by 3, then m will equal 2 times that number. m=2(n-3) The second clue says that m is 4 plus n. m=n+4

Since we know that m=2(n-3) and m=n+4 2(n-3) must also equal n+4 since they are both equal m. So, 2(n-3)=n+4. Simple algebra 2(n-3)=n+4 (multiply n and -3 by 2) 2n-6=n+4 (subtract n and add 6 on both sides) n=10, So Nora is 10 which means m=10+4, So Mary is 14

Plug both back into each equation and it all checks out m=2(n-3) m= n+4 m=14 n=10 14=2(10-3), 14=20-6, 14=14 14=10+4, 14=14

Make sense?

Ashley Gardner - 3 years, 7 months ago

Awesome, thanks

A Former Brilliant Member - 3 years, 7 months ago

No problem

Ashley Gardner - 3 years, 7 months ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$