I don't know if this answer will still help you or not, seeing as you posted this 4 days ago, but anywayyyy
We use the Pythagorean Theorem here. (a² + b² = c²)
5² + 12² = c²
25 + 144 = c²
169 = c²
13 = c
The length of the hypotenuse is 13 cm.
Hope that helped even though this is late :)
