2(x-3y)-3(2x-y)
=2x-6y-6x+3y
=-4x-3y
(8a-7b)-2(2a-3b)
=8a-7b-4a+6b
=4a-b
2a-[a+(2a-2)]
=2a-(3a-2)
=2a-3a+2
=-a+2