四分之三乘五分之二+百分之二十乘四分之三+零点七五×零点四 3/4 × 2/5 + 20/100 × 3/4 ＋ 75/100 ×4/10= 3/4 × 2/5 +1/5 × 3/4 ＋ 3/4 × 2/5=3/4 （ 2/5 +1/5 ＋ 2/5）=3/4
