You can find the missing side of a right triangle by using the Pythagorean Theorem (a² + b² = c²), where c is the hypotenuse. So, just plug the given numbers in and solve for c.
a² + b² = c² Plug 6 and 8 in for a and b (order doesn't matter)
6² + 8² = c² Square both numbers
36 + 64 = c² Add
100 = c² Take the square root of both sides
10 = c Switch the sides of the equation to make it easier to read
c = 10
So, the hypotenuse of the triangle is 10 cm.