ax + z = aw - y
ax - aw + z = -y Subtract aw from both sides.
ax - aw = -y - z Subtract z from both sides.
a(x - w) = -y - z Factor ax - aw.
a = (-z - y)/(x - w) Divide x - w froem both sides.
a = (-1(y + z))/(x - w) Change the solution.
a = -(y + z)/(x - w)