The difference in age between Joel and his dad is 32 - 5 = 27 years. When you double this gap in years, you have 27 x 2 = 54. When his dad is 54, Joel will be 54 / 2 = 27 years old.
This justifies what answer for what question? Q & A:
Joel is 5 years old and his dad is 32 years old. How old will Joel be when his dad is twice as old as him?
27