a) 8x+7+2x-6y-2y=10x-8y+7
b) 9-4a+6b+7a-6-a=2a+6b+3
c) 1-p+4-5p-2r+6p+r= -6p+6p-r+5=5-r
d) 4xy-2x-3y+8x-xy-2x=3xy+4x-3y
