The starting number is
y = 0
y = 8
The number that is added each time is
4, which becomes the slope, because repeatedly adding the same number can be shortened to multiplying by that number
4, which becomes the y-intercept, because the y-intercept is added on
The formula is
y = 4 + 8x
y = 8 + 4x
When x = 6, using the formula, we get
28 + 4 = 32
y = 8 + 4(6) = 32