15 I may be wrong but If I am please provide more information.
Answer:
31.25×
Step-by-step explanation:
suppose that the value of x was 3 . that would mean that they bought 3 calculators .
if one calculator is $31.25 then 3 would be $31.25× 3
the same rule would apply for x
The differnce quotient is basically taking the derivitive (result will be f'(x)=5, but anyway)
here is the disffernce quotient

so
for your equation



h's cancel and you are left with 5
the differnce quotient is 5
Answer:
D.
Step-by-step explanation:
The number which multiplies x is the slope of the graph so 13x becoming 3x means the slope of the graph will change.