42) 9/10 * [7/8 / (4/5 + 1/4)] = 3/4。43) 408 * 25 / 50 = 204。44) 1.92 / 0.8 * 1.25 = 3。45) 13/4 * 8/7 / 26/5 = 5/7。46) (11/5 * 23/7 - 3/2) * 7/2 = 25/4。47) 5/2 * [3/50 * (1/2 - 1/3)] = 10。48) 7/8 * 56 + 44 * 7/8 = 700/8。49) 4678 + 3420 / 36 = 4773。50) 4.5 * 3.7 - 5.74 - 4.26 = 6.65。51) 8/49 * [3/4 - (3/16 + 1/8)] = 1/14。