甲数是4分之3,乙数比甲数少3分之2,丙恰好是甲乙两书的一半，丙数是多少?

甲数是(3/4),乙数比甲数少(2/3),丙恰好是甲乙两数和的一半，丙数是多少?
甲数是(3/4)
乙数是(3/4)-(2/3)=9/12-8/12=1/12
丙数是((3/4)+(1/12))/2=(9/12+1/12)/2=(10/12)/2=5/12

11.2减去4.6的差,乘25加上16的积,积是多少?
(11.2-4.6)*(25+16)=6.6*41=270.6

12分之5与它倒数的和减去8分之1乘3分之2的积，所得的差被20分之1除，结果是多少？
((5/12+12/5)-(1/8)*(2/3))/(1/20)
=((25/60+144/60)-(1/12))/(1/20)
=((169/60)-(1/12))/(1/20)
=((169/60)-(5/60))/(1/20)
=(164/60)/(1/20)
=(164/60)*20
=164/3
=54又(2/3)

3分之2除以9分之4的商去除2乘5分之4的积，所得的差被20分之1除，结果是多少？
(2/((2/3)/(4/9)))*(4/5)/(1/20)
=(2/((2/3)*(9/4)))*(4/5)/(1/20)
=(2/(3/2))*(4/5)/(1/20)
=(2*(2/3))*(4/5)/(1/20)
=(4/3)*(4/5)/(1/20)
=(16/15)/(1/20)
=(16/15)*20
=64/3
=21又(1/3)