a) 2x -3 + 4x-7 = 6x - 10
b) 2x-3 - 4x-7= - 2x - 10
c) 2x-3 +4x-7 + 6x-5 = 12x - 15
d) 2x-3 + ( 4x-7 - 6x-5) = 2x - 3 + ( -2x - 12 ) = 2x -3 - 2x - 12 = - 15
e) -2x-3 + 4x-7 - 6x-5 = - 4x - 15
f) ( 2x-3 - 4x-7) + ( 4x-7 - 6x-5 ) + ( 6x-5 - 2x-3 ). = - 2x - 10 - 2x - 12 + 4x-8= -30