If Shannon's age is exactly half of Josh's age, what is Shannon's age?

[BTGModeratorVI]

If Shannon's age is exactly half of Josh's age, what is Shannon's age?

(1) Six years ago Josh's age was exactly three times Shannon's age.
(2) Twelve years from now, Josh's age will be exactly 1.5 times Shannon's age

Answer: D
Source: Veritas

[Brent@GMATPrepNow]

If Shannon's age is exactly half of Josh's age, what is Shannon's age?

(1) Six years ago Josh's age was exactly three times Shannon's age.
(2) Twelve years from now, Josh's age will be exactly 1.5 times Shannon's age

Answer: D
Source: Veritas

Target question: What is Shannon's age?

Given: Shannon's age is exactly half of Josh's age
In other words, Josh is CURRENTLY 2 times as old as Shannon.
So, if we let x = Shannon's CURRENT age,...
...then 2x = Josh's CURRENT age

Statement 1: Six years ago Josh's age was exactly three times Shannon's age.
x - 6 = Shannon's age SIX YEARS AGO
And 2x - 6 = Josh's age SIX YEARS AGO
SIX YEARS AGO, Josh's age was exactly three times Shannon's age
We can write: 2x - 6 = 3(x - 6)
Expand: 2x - 6 = 3x - 18
Solve..... x = 12
The target question is Shannon's CURRENT age is 12
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: Twelve years from now, Josh's age will be exactly 1.5 times Shannon's age.
x + 12 = Shannon's age TWELVE YEARS FROM NOW
And 2x + 12 = Josh's age TWELVE YEARS FROM NOW
TWELVE YEARS FROM NOW, Josh's age will be exactly 1.5 times Shannon's age
We can write: 2x + 12 = 1.5(x + 12)
Expand: 2x + 12 = 1.5x + 18
Solve..... x = 12
The target question is Shannon's CURRENT age is 12
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,
Brent