give a counterexample. In each case, w / 0. (a) If u w = v w holds, then u = v. (b) If u xw=vx w holds, then u = v. (c) If u w = v. w and uxw = v x w both hold, then u = v. Hint for (c): You can rewrite u w = v w as (u-v) w = 0. What does this tell you about u-v? Similarly, you can rewrite uxw=vxw as (u-v) xw = 0. What does this tell you about u-v? How can both things be true at the same time?