The point-slope form is:

So, here, you just plug in values:

It would be + 1 because remember, the '-' sign just means the opposite of, not subtraction in this case. Also, m = slope.
H = -2r + s/πr
C = 3A-a-b
If you need step by step comment
The answer is 1/4 since 4 quarts make 1 gallon.