（0.75-3/16）*（2/9+1/3）= (12/16-3/16)*(2/9+3/9)
=(9/16)*(5/9)=5/16
18/35除以0.6*2/3=(18/35)*(5/3)*(2/3)=4/7
35/64除以（1/8+3/4）=(35/64)÷(7/8)=(35/64)*(8/7)=5/8