Given that x : y = 7 : 4 and x + y = 88, calculate x - y.

From x : y = 7 : 4 work out an expression for x: x = y (7/4) and substitute into x + y = 88: y(7/4 + 1) = 88y( 11/4) = 88 y = 88 (4/11) = 8 x 4 = 24substitute this into x + y = 88 to get x = 88 - 24 = 64.
x - y = 64 - 24 = 40.