I believe it's 32 since side one is 10 cm, side 2 is 8 cm, and with the Pythagorean Theorem (a^2+b^2=c^2) the diagonal side is somewhere between 12 and 14 cm. Adding everything up yields an answer closest to 32 cm.
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.
