Top-right: 12/15 is 0.8
Bottom-middle: I think it can be written as log(26)/log(3) = 2.96
Top-left: Square root of 20 is about 4.48
Top-middle: 3 factorial is 3*2*1=6
Middle-right: e squared is about 7.39
Bottom-right: 7*pi/2 is about 11
Center: The sigma notation is 1+2+3+4+5=15
Middle-left: Infinity
I don't remember how to do integrals (bottom-left) so you can try to brute force that one, starting with the 2nd highest, then 3rd highest, etc.
Delicious and vicious, while maliciously nutritious.