Trinh is catering a wedding that 112 people will attend. She is making two cakes, a chocolate cake and a carrot cake. of the guests will be served chocolate cake and the rest will receive carrot cake. How many guests will get carrot cake?

The answer is

Use pythagorean’s theorem and find the missing side lengths of the two smaller triangles and add them together
13^2 - 12^2 = 5
15^2 - 12^2 = 9
5+9 = 14
14 is the length of each side of the square
14^2 + 14^2 = 19.8
19.8 is the diagonal length of the inside if the square