Explanation:
in such a case the easiest approach might be using the point-slope form of a line equation :
y - y1 = m(x - x1)
with m being the slope, and (x1, y1) being a point on the line.
so, in our case that would be
y - 8 = 8(x - 4)
simplified this would be
y - 8 = 8x - 32
y = 8x - 24
FYI - this would be then the slope-intercept form (-24 would be the intercept point on the y-axis).