Hello,
I assume that the slope of the line is
Use the point-slope-formula. If you know the coordinates of point and the slope m then the equation of the line is:
. Plug in the values you already know and solve for y.
Second attempt: The general form of an equation of a straight line is:
. The coordinates of the given point must satisfy this equation. You know m already. Plug in these values and solve for b: