To find the length of the missing side, you can use the Pythagorean Theorem, which you can only use for right triangles.
Pythagorean Theorem: a² + b² = c²
[ c is the hypotenuse or the longest side of the triangle, and a and b are the other sides, I think it doesn't matter which side ]
Plug in what you know:
b = 8
c = 14
a² + b² = c²
a² + (8)² = (14)²
a² + 64 = 196 Subtract 64 on both sides
a² = 132 Square root both sides to get "a" by itself
a = inches
If you need to simplify more, you need to find two numbers that multiply to = 132 where one of them can be square rooted, to do so you can list the greatest common factors of 132
132: 1, 2, 3, 4, 6, 11, 12, 22, 33, 44, 66, 132
The only number that can be square rooted is 4, so you can do: