Answer:
1)
The hypotenuse is the longest side of a triangle. It is ALWAYS the one across from the right angle (depicted as the box in the corner at 90 degrees). Therefore the 2 sides that intersect the 90-degree angle are "leg" and "leg" and the longest side is the"hypotenuse"
2)
The Pythagorean theorem states:
where a and b are sides and c is the hypotenuse.

For your purposes, a and b do not matter which number you choose as long as you make sure that they are sides and not the hypotenuse.
3)
The Pythagorean theorem states:
where a and b are sides and c is the hypotenuse.

Hope that helps!