1、(1-3*(1/12+1/15))÷(1/15+1/10)
=(1-9/20)÷1/6
=11/20*6
=33/10
(1-3*1/12)÷(1/15+1/10)
=(1-1/4)÷1/6
=3/4*6
=9/2
(1-3*1/12)÷(1/10+1/12+1/15)
=(1-1/4)÷(1/4)
=3/4*4
=3