Since we are solving for b, you need to get it by itself. So you would divide both sides by 3a. That would leave b= -7/3a.
Hope this helps!!
Big town is 5.121 times larger than Small town.
Step-by-step explanation:
Step 1:
In order to determine how much larger Big town's population is to Small town's population is, we need to convert the exponentials into actual numbers.
Small town's population 
Big town's population 
Step 2:
In order to determine how much larger Big town's population is to Small town's population is, we divide Big town's population by Small town's population.

So Big town is 5.121 times larger than Small town.