25ab-(-3ab)
8am-3am
7abc-3abc
5bc+(-5bc)
7mn+3mn
2a+3a
20xy/4xy
6xyz+10xyz
4xy-2xy
(4cd)(10cdx)
5a
10mn
2xy
28ab
40c^2d^2 x
5xy
5am
16xyz
4abc
0
