32 because if you take the left side and the bottom side you have a and b, so you can use the pothagorean theorem. The pothagorean theorem is
{a}^{2} + {b}^{2} = {c}^{2}
So then you can plug in what you have, and you would get
{10}^{2} + {8}^{2} = {c}^{2}
Then you should simplify to get 100+64=c^2. Then you should simplify some more to get c^2=164. Then you should take the square root of each side to get c is about 13. Then all you have to do is add 10, 8, and 13 to get 31 which is closest to 32.