Example C: w cubed z, +, 5, z squared, minus z squared, +, 6 ..... For example, 2x + 1 = 7x and 10x minus 9y minus z = 3 are linear equations, but x, +, y ...
If you have 9 divers total and each team can only have 4 divers, then logically the US can select 2 teams of 4 from 9 divers.
63 degrees, if that angle is 72 that means the other must be 54 (add to 180), and if that angle on the other triangle is 54, the others must be 63 (add to 180).