9.8 = 10 - 0.2
原式 = 10 *7.4 - 0.2 * 7.4
= 74 - 1.48
= 72.52还有一题是36.1*8.5+39*0.85，刚刚漏了还有一题是36.1*8.5+39*0.85，刚刚漏了39 * 0.85 = 3.9 * 8.5所以原式 = (36.1+3.9) * 8.5 = 40 * 8.5 = 340