Answer:
A. add -15 and 9
Step-by-step explanation:
We follow the PEMDAS rule as the order of operations to evaluate expressions.
P-Parenthesis
E-Exponents
M-Multiplication
D-Division
A-Addition
S-Subtraction
Given expression : 
In order to evaluate the expression, the first step would be to do the parenthesis operations which requires to add -15 and 9.
I think 7a^3b^6, but im not sure so im sorry if it is wrong
The function best models the linear relationship is y=12,000x+40,000.