Answer:
We are finding hypotenuse
3^2 + 2.5^2
9 + 6.25 = 15.25
3.9^2 = 15.21 close enough.
3.9 would be your answer.
When finding the hypotenuse, we square the two given lengths add them up and then that number you get from adding them up, there should be a number that will be squared that will equal that number that you added up.