Two legs of a right triangle each measure 10 inches how long is the hypotenuse

For this case, the first thing you should do is apply the Pythagorean theorem:
 c = root ((a) ^ 2 + (b) ^ 2)
 Where,
 a, b: sides of the triangle
 c: hypotenuse
 Substituting values we have:
 c = root ((10) ^ 2 + (10) ^ 2)
 c = root (100 + 100)
 c = root (200)
 c = root (2 * 100)
 c = 10 * root (2)
 Answer
 The hypotenuse is:
 c = 10 * root (2) inches

The first answer is correct