Really out of time I need answers fast

answer:

-3

Step-by-step explanation:

c is y when x = 0

At x = 3, y = 21-9 = 12

At x = 2, y = 12 - 7 = 5

At x = 1, y = 5 - 5 = 0

At x = 0, y = 0 - 3 = -3

c = -3

If you don't get this, make three equations using any three coordinates (from the given points) and solve the equations simultaneously for the unknowns, a b and c

The value of c is most likely 2.

I found this because I noticed a pattern:

32 - 21 = 11

45 - 32 = 13

60 - 45 = 15

77 - 60 = 17

Each of these is being added by 2.