54乘20分之1加45除20加20分之1
=54+ 1/20 + 45 * 1/20 + 1/20
=(54+45+1)* 1/20
=100* 1/20= 5
（6分之1加8分之1加24分之1）乘24
=1/6 *24+ 1/8*24+ 1/24 *24
=4+3+1
8