a = b + 160 (1) a - 0.1a = 3*(b + 0.1a) (2) Equation (2) is equivalent to 0.9a = 3b + 0.3a or 0.9a - 0.3a = 3b, 0.6a = 3b (3) From eq(1), substitute a = b+160 into eq(3). 0.6*(b+160) = 3b 0.6*b + 0.6*160 = 3b 0.6*160 = 3b - 0.6b 96 = 2.4*b b == 40. ANSWER. Beta started with £40; Alpha started with £40 + £160 = £200. CHECK. 200 - 20 = 180; 40 + 20 = 60. 180 is three times 60. ! Correct !