The formula y-y1=m(x-x1) is known as the point-slope form to graph a line. Solve this formula for x.

Answer 1

x = (y-y1)/m + x1

Answer 2

y-y1=m(x-x1)
y - y1 = mx - mx1
y - y1 + mx1 = mx

x = (y - y1 + mx1)/m