In a hand of cards, the ratio of black cards to red cards was 5 to 3. If the hand contained 15 black cards, which of the following proportions could be solved to find the number of red cards, r? (1) 15 5 3 r  (3) 3 15 8 r  (2) 5 15 3 r  (4) 15 5 8 r 