8/9 * 3/4 = 2/3
(1/3-1/4) + 1/3 * 1/4 = 1/12 + 1/12 = 1/6
7/24 * 3/7 + 7/8 = 1/8 + 7/8 = 1
( 9 + 1/9 ) * 7/9 = 82/9 * 7/9 = 574/81
