Verified Answer :

y = mx + c

If y = 4, and x = 0, then:

4 = -1 (0) + c

c = 4

If c = 4:

y = -1 (2) + 4

y = -2 +4

y = 2

If you plug in the different values of x in each equation, the answer should be:

2,0,-2

We know, the principle equation of line, 
y = mx + c
when, x = 0, y = 4, c =?
4 = (-1)(0) + c
c = 4
When, x = 2, y = (-1)(2) + 4 = -2 + 4 = 2
x = 4, y = (-1)(4) + 4 = -4 + 4 = 0
x = 6, y = (-1)(6) + 4 = -6 + 4 = -2

In short, Your Answers would be 2, 0, -2

Hope this helps!