Would surely like to see you begin the problem solution yourself and to share what you have done.
Let the girl's age be J and the father's F.
J=5 and F=42 now.
In x years, the father will be twice as old as the girl.
We write that as F + x = 2( J + x), or 42 + x = 2( 5 + x)
Then 42 + x = 10 + 2x => x = 32
check: is 42+32 = 2(5+32)? Is 74 = 2(37)? YES.
The answer: "5 years from now."
