Final answer:
The correct answer is c. 45/37.
Step-by-step explanation:
The equivalent ratios are 15/5, 5 is to 3, and 2.5:4.5. To determine which ratio is not equivalent, we can compare them to the remaining option, 45/37. If we simplify each ratio, we find that:
15/5 = 3
5 is to 3 = 5/3
2.5:4.5 = 5:9
However, 45/37 cannot be simplified further. Therefore, the correct answer is c. 45/37.