Answer:
1. The cost increases $0.30 each time 1 goldfish is
added.
Answer:
(9/2, 7/2)
Step-by-step explanation:
The easiest way to remember how to do this problem is to average the x-coordinates and average the y-coordinates.
So, in your problem (-3 + 12)/2 = 9/2 and (-5 + 12)/2 = 7/2
The midpoint is (9/2, 7/2)
If you want to multiply the two functions, the answer is a.
In fact, you have

-15 and -42 both add to -57 and multiply to 630
X + x + 165 = 1315
2x + 165 = 1315
subtract 165 from both sides
2x = 1150
divide both sides by 2
x = 575
January 575
February 575 + 165 = 740