Why is x = 4 a solution to the proportion 15/x = 56/16 a) because 56 divided by 14 equal to 4. b) because 56 divided by 16 is equal to 4. c) because if you substitute 4 into the equation for x and cross multiply, you get 196 = 196. d) because if you substitute 4 into the equation for x and cross multiply, you get 224 = 224