Consider something like 2b+6 factoring to 2(b+3). When we distribute that outer 2 back inside the parenthesis, we're multiplying that 2 by everything inside. Factoring goes in reverse of this and we divide each term of 2b+6 by the GCF 2.
The same thing applies to this current problem as well.
Divide each term by the -1.8 we want to factor out.
(3.6b)/(-1.8) = -2b
(-9)/(-1.8) = 5
The results -2b and 5 will go inside the parenthesis. That's how we end up with -1.8(-2b+5)
