Stuck

Hi oquiella,

You should notice that the answer choices all include the variable Y; they're all written "in terms of Y."

This question can be solved with Algebra or by TESTing VALUES. Here's how to TEST VALUES...

We're given two facts to work with:
1) The sum of Doris's and Fred's ages is Y
2) Doris is 12 years old than Fred

IF....
Fred = 2
Doris = 14
Y = 2+14 = 16

We're asked how old Fred will be Y years from now. Fred is now 2; in 16 years, he'll be 18. Thus, we're looking for an answer that equals 18 when Y = 16. There's only one answer that matches....

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

oquiella wrote:The sum of the ages of Doris and Fred is y years. If Doris is 12 years older than Fred, how many years old will Fred be y years from now, in terms of y?

A. y - 6
B. 2y - 6
C. Y/2 - 6
D. 3Y/2 - 6
E. 5Y/2 - 6

Rich has demonstrate the input-output approach.
The algebraic approach is a little more complicated, but let's try it.

Doris is 12 years older than Fred. In other words, Doris' age = (Fred's age + 12).
So, the sum of their ages = (Fred's age) + (Fred's age + 12)
Simplify to get: sum of their ages = 2(Fred's age) + 12
We're told that the sum of the ages = y, so 2(Fred's age) + 12 = y
Now solve for Fred's age.
2(Fred's age) + 12 = y
2(Fred's age) = y - 12
Fred's age = (y - 12)/2
Fred's age = y/2 - 12/2
Fred's PRESENT age = y/2 - 6

How many years old will Fred be y years from now, in terms of y?
This equals y/2 - 6 + y

When we check the answer choices, we don't see y/2 - 6 + y, so we need to SIMPLIFY

y/2 - 6 + y = y/2 - 6 + 2y/2 (get common denominator of 2)
= 3y/2 - 6
= D

Cheers,
Brent

Rich and I have demonstrated the two methods (Algebraic and Input-Output) for solving a question type I call Variables in the Answer Choices.
If you'd like more information on these approaches, we have some free videos:
- Variables in the Answer Choices - https://www.gmatprepnow.com/module/gmat- ... /video/933
- Tips for the Algebraic Approach - https://www.gmatprepnow.com/module/gmat- ... /video/934
- Tips for the Input-Output Approach - https://www.gmatprepnow.com/module/gmat- ... /video/935

Cheers,
Brent