The slope is (difference in 'y') divided by (difference in 'x') .
Difference in 'y' = (9 - 4) = 5
Difference in 'x' = (4 - [-1]) = 5
Slope = 5/5 = 1 .
(I don't think we need the pictures at all.)
You are given the function 
Express t:

This expression gives the month t in terms of the price p.
You combine like terms.
-2x+9x
whatever answer that is you then combine the like terms -9+-1 the you just make an expression out of them.
Answer: I would think
6-0
12-1
30-2
Step-by-step explanation: