(a) If Musa's age = x and Manya's age = y, then x = y + 3.... (1) and (x — 7) = 2(y— 7) .......(2) Solving both equations will yield Musa's age = 13 years and Manya's age = 10 years. (b) Let n be the year when the sum of their ages will be 45, so that (10 + n) + (13 + n) = 45 and solving will give n = 11 years.