Answer:
Yes it is proportional
Step-by-step explanation:
If an equation like this one has a constant rate of change then it is. that means that if the ratio always stays the same and never changes, it will be proportional.
I think the pdf image can give you the answers you are looking for.

Let's start off by writing this with symbols. 
Follow the order of operations and start with the exponent. 
Now, solve the parentheses. 
Multiply. 
Add. 

the rectangular prism's volume has to multiply up to 20,000.... so one possible would be 10 feet high, 100 feet long, and 20 feet wide
Answer:
8
Step-by-step explanation:
12.50(8) =100 +20 = 120