Since we know that the line crosses the x axis, we can assume that the value of Y at this point is 0. So we must substitute y = 0 into the equation y = 2x + 40 = 2x + 4we now have to isolate x on its own so we -4 from both sides of the equations as we want to get rid of it on the right hand side -4 = 2x and now we have to divide both sides by 2 in order to get x on its own -2 = x so the value of x at point R is -2