Step-by-step explanation: First, Kevin cut a plank a yard long. That means that he has a plank thats a yard long. Next, he painted 1/3 of the plank black. Before, 3/3 (basically equals to 1 yard long) of the plank was unpainted. So, the equation will be 3/3 - 1/3 which is equal to 2/3 yard.
