Problem Solving

swerve wrote:Today Rebecca, who is 34 years old, and her daughter, who is 8 years old, celebrate their birthdays. How many years will pass before Rebecca's age is twice her daughter's age?

A. 10
B. 14
C. 18
D. 22
E. 26

The OA is C

Source: Official Guide

I think the best (i.e., fastest) approach is to TEST the answer choices.
However, for those who prefer using algebra, here's an algebraic approach:

Let x be the number of years from today.
So, x years in the future, Rebecca's age will be 34 + x
And, x years in the future, her daughter's age will be 8 + x

We want Rebecca's future age to be twice her daughter's future age.
We can create the following "word equation": (Rebecca's future age) = 2(daughter's future age)
Or we can write: (34 + x) = 2(8 + x)
Expand to get: 34 + x = 16 + 2x
Solve to get: x = 18

Answer: C

Cheers,
Brent