1(2/9 * 4/7 + 7/9)/(7/4) = (2/9 * 4/7)/(7/4) + (7/9)/(7/4) = 32/441 + 4/9 = 76/1412(1/10 + 3/4)/(5/6) = (1/10)/(5/6) + (3/4)/(5/6) = 3/25 + 9/10 = 51/503(2/3)/（5/6+1/4）= (2/3)/(11/12) = 8/11