Answer:
The length of the third side is equal to 10.
Explanation:
In order to solve this, we need to know that in a right-angled triangle, the following is true:
(where "c" is the hypotenuse and "a" and "b" are the legs of the right-angled triangle)
Now we can find the length of the missing side, lets say that the leg that we are trying to find is "a", then after plugging in the information we know, we get the following:

Therefore, the length of the third side is equal to 10.