3乘(15分之2+12分之5)-3分之2
=3×2/15+3×5/12-2/3
=2/5+5/4-2/3
=(24+75-40)/60
=59/60
4分之3*6分之5-10分之3除以12
=5/8-3/10×1/12
=25/40-1/40
=24/40
=3/5
12*5*(5分之1+12分之1)
=12*5*1/5+5*12*1/12
=12+5
=17