a - 1 3/4 = 2 1/2 a = ? a = 2 1/2 - 1 3/4 = 2 2/4 - 1 3/4 = 1 6/4 - 1 3/4 = 1 3/4 2 1/2 = 2 2/4 a = 1 3/4