Mario has 20 yards to mow this week. By Wednesday, he had mowed 50% of the yards. How many yards had he mowed by Wednesday?

50% means one-half. Half of 20 yards is 20 ÷ 2 = 10 yards, so Mario had mowed 10 yards by Wednesday. The correct choice is C, 10.

AI-written and checked against the verified answer.