4分之3*(5分之2-3分之1)+8分之7/2分之1
=3/4*(2/5-1/3)+7/8/(1/2)
=3/4*(6/15-5/15)+7/8*2
=3/4*1/15+7/4
=1/20+7/4
=1/20+35/20
=36/20
=9/5