First, calculate the gradient of the line (m) using the equation using dy / dx.m = dy / dx = (y_2 - y_1) / (x_2 - x_1) = (12 - 4) / (8 - 4) = 8 / 4 = 2.As you now know the gradient of the line and points on the line, it is possible to substitute values in to the equation y = mx + c.For point A (4,4):y = mx + c 4 = 2 * 4 + c 4 = 8 + c4 - 8 = cc = -4Therefore, the equation of the line is:y = 2x -4