[tex]y_2-y_1=m(x_2-x_1)\ \ \ \ |divide\ both\ sides\ by\ m\neq0\\\\x_2-x_1=\dfrac{y_2-y_1}{m}\ \ \ \ \ |add\ x_1\ to\ both\ sides\\\\\boxed{x_2=\dfrac{y_2-y_1}{m}}\\\\x_2-x_1=\dfrac{y_2-y_1}{m}\ \ \ \ |subtract\ x_2\ from\ both\ sides\\\\-x_1=\dfrac{y_2-y_1}{m}-x_2\ \ \ \ \ |change\ signs\\\\\boxed{x_1=x_2-\dfrac{y_2-y_1}{m}}[/tex]
