If John is x years old now, and his father is 44 years old now

[BTGModeratorVI]

If John is x years old now, and his father is 44 years old now, in how many years will John’s father be twice as old as John will be at that time?

A. 44 – 2x
B. 44 – x
C. 44
D. 2x
E. x – 22

Answer: A
Source: Official guide

[Brent@GMATPrepNow]

If John is x years old now, and his father is 44 years old now, in how many years will John’s father be twice as old as John will be at that time?

A. 44 – 2x
B. 44 – x
C. 44
D. 2x
E. x – 22

Answer: A
Source: Official guide

GIVEN:
x = John's PRESENT age
44 = the father's PRESENT age

Let k = the number of years it will take until John's father is TWICE as old as John

So....
x + k = John's age IN k YEARS
44 + k = the father's IN k YEARS

In k years, we want the father's age to be twice John's age
In other words we want: 44 + k = (2)(x + k)
Expand to get: 44 + k = 2x + 2k
Subtract k from both sides to get: 44 = 2x + k
Subtract 2x from both sides to get: 44 - 2x = k

In other words, in 44 - 2x years, the father's age will be twice John's age

Answer: A

Cheers,
Brent