c) 7u-12-6c=-6c+7u-12
7c-12-6c=c-12
d) 121-51-17y=70-17y
e) 25+2(12-3x+21)=25+24-6x+42=91-6x
f) (5-4x+36)-40=41-4x-40=1-4x
g) (25x-3+3y-z)=25x+3y-z-3
c) 7u-12-6c=-6c+7u-12
7c-12-6c=c-12
d) 121-51-17y=70-17y
e) 25+2(12-3x+21)=25+24-6x+42=91-6x
f) (5-4x+36)-40=41-4x-40=1-4x
g) (25x-3+3y-z)=25x+3y-z-3