Do the coefficients first. Since 5 is a factor of 15, it is automatically the GCF. Choose the lowest power of the common variables. The GCF is 5b.
60b2 you multiply the coefficients then the exopnients 5b1 (next to variables there are invisible exonients) x 12b1 ______ 60b2 (when multiplying like variables you add the exponients)
5b + 5b = 2 x 5b
The GCF is 5b.
9a-99 = -90
It is the same as: 9a -4a = 5a
It is: 9a-a-a = 7a
2a+5b isn't possible the answer is still 2a+5b.
5b-15 = -10
9a - 8a = a
If: 9a = 18b Then: a = 2b
15 = 5b