x+x+x-x-x-x
2x+3x+4x+5x
2xy+3y-2x+4xy+5x-8y
3b-b
3a+4b-2a-b
a+a+a+a
m+n+m+n+m+n
3n+5m-5n+10m
14x
4a
2b
3m+3n
0
6xy-5y+3x
-2n+15m
a+3b
