5,12,13 is a common Pythagorean triple, the second on the list after 3,4,5
B and C aren't on the list, and they would be if they were Pythagorean Triples, which is a list of natural number length sides (a,b,c) which satisfy the Pythagorean Theorem, a²+b²=c², making them the sides of a right triangle.
Each box represents 1/3. 5/3 of white is 2 boxes more so red needs 2 boxes more than white. 5 red and 3 white is the only one that follows the criteria.
