Answer:
16.5
Step-by-step explanation:
Just put in the values of C and y first into the expression.
C = 4x + 5y
Put in values.
51 = 4x + 5(-3)
Evaluate.
51 = 4x + (-15)
Swap positions.
4x + (-15) = 51
Shift (-15) to the other side and change to (+15).
4x = 51 + 15
= 66
Find x.
x = 66 ÷ 4
x = 16.5