What 4 consecutive whole numbers add to 54

If X is the first consecutive whole number, (X+1), (X+2) and (X+3) are the others.

So we know:
X + (X+1) + (X+2) + (X+3) = 54
X + X+1 + X+2 + X+3 = 54
4X + 6 = 54
4X = 48
X = 12

So the numbers are 12, 13, 14 and 15

D) the x-intercept represents adam's commission pay when he had zero total sales