Ok lets break this problem into 3 easy parts and combine the like terms:
2ab-8ab,
-7cd+3cd,
and -6ef-4ef.
1. Solve 2ab-8ab, which is -6ab.
2. Solve -7cd+3cd, which is -4cd.
3. Solve -6ef-4ef, which is -10ef.
4. Now combine the 3 problems into 1 problem again, which would be -6ab-4cd-10ef
2ab-8ab-7cd+3cd-6ef-4ef = -6ab-4cd-10ef
{Math Check}
(The letters are left out in the imputs, because the imputs won't work correctly with the letters included, but for all practical purposes the math will still be true.)
2ab-8ab
[input]2-8[/input]
-7cd+3cd
[input]-7+3[/input]
-6ef-4ef
[input]-6-4[/input]