15a+9b-6a-2b
4(3x+5y)
20x-4(2y+4x)
17b-5(a+3b)
12x+20y
6x+7y
8x+2y-2x+5y
4a+5b+3a+7b
7x+14y
3(6a-5b)-8a
2x+2y
10a+14b
-5a+2b
2(5a+7b)
9a+7b
4x-8y
10a-15b
6a-18b
7(x+2y)
3x+6y-x-4y
6(a-3b)
7a+12b
