(4/15-1/5)*25 (7/12+5/36):13
(4/15 - 1/5 ) * 25 = (4/15 - 3/15 )*25 = 1/15 * 25 = 1/3 *5 = 5/3 = 1 2/3 ==================== (7/12+5/36)/13 = (21/36 + 5/36) = 26/36 * 1/13 = 2/36 = 1/18