The present age of J is twice the age of A. After 5 years, the ratio of the ages of J and A will be 7 : 4. What will be the age of J after 7 years?
37
37 is correct.
Let A's present age be x years; then J's present age is \(2x\) years.
After 5 years: \(\dfrac{2x + 5}{x + 5} = \dfrac{7}{4}\), so \(8x + 20 = 7x + 35\), giving \(x = 15\).
J's present age \(= 2 \times 15 = 30\) years, so after 7 years J will be \(30 + 7 = 37\) years old.