Word Problem

ECBERNA

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Oct 10, 2011
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Can anyone help me with this problem.

In 3 years David will be twice as old as he was last year, How old is David now?
 
x+3=2(x-1)
x+3=2x-2
x+5=2x
x+5-x =2x-x
5=x

So 5+3=8
5-1=4
He is 5
 
Hello, ECBERNA!

In 3 years David will be twice as old as he was last year.
How old is David now?

Set up some relations.

Let x\displaystyle x = David's age now.

In 3 years, he will be 3 years older: .x+3\displaystyle x+3

And last year, he was one year younger: .x1\displaystyle x-1


Now translate the English into Algebra:

. . In 3 yearsx+3will be=twice2×last year(x1)\displaystyle \underbrace{\text{In 3 years}}_{x+3} \:\underbrace{\text{will be}}_{=}\: \underbrace{\text{twice}}_{2\:\times}\: \underbrace{\text{last year}}_{(x-1)}


There is our equation! .. . x+3=2(x1)\displaystyle x + 3 \:=\:2(x-1)

Got it?
 
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