Give me an equation of the line passing through the points (8,1) and (8,-7)

The normal line format is y=mx+b

m = the slope, and we will start by finding the slope
the slope =Δy/Δx = rise/run = the change in y over the change in x
(-7)-1 / 8-8 = -8/0 when the denominator is zero, the slope is undefined, meaning it is a perfectly vertical line

b is the y intercept. the y intercept is where the line crosses the y axis, we have a  vertical line at the x coordinate 8, which means there is no y intercept

at this point it is easies to look at the points we have. the x coordinate is always 8, there is no y-intercept, and the slope is undefined, this means we can write the equation of the line as x=8