Please help, this one had me upset all day!

7, 24, 25 makes one. 9, 40, 41 as well. 39, 52, 65 works. 11, 60, 61 does too. Lastly, 40, 42, 58 is a right triangle as well. 

How I found out was plugging each into the Pythagorean Theorem for proving/solving right triangles of a² + b² = c². The last number in each combo is your C. The other two numbers are interchangeable in regards to position.