If you know that the equation for a line has slope m, and that it passes through the point (x1, y1), then it's equatoin is:
So here you have:
y-8 = 17.77(x-1)
Which you can rearrange into y = mx+b form:
y = 17.77(x-1) + 8.
y = 17.77x -9.77
The y-intercept of the line is therefore: -9.77