Margaret bought one child fair ticket and one adult fair ticket for a total of $56. A child ticket cost $12. Which equation can Margaret use to find x, the cost of an adult ticket?

Responses
A 12 + x = 5612 + x = 56
B x – 12 = 56x – 12 = 56
C 12x = 5612 x = 56
D 12 ÷ x = 56