C stands for combination. C is 3 in the upper right corner and 5 in the lower right corner, that is to say, how many permutations and combinations of three things are selected from five things (in no particular order)?

Calculation method: 5! /3! *(5-3)! = 1*2*3*4*5/ 1*2*3* 1*2= 10

Along any two sides, greater than the third side.

That is, the combination of three numbers selected from five numbers is 10, minus the invalid (3,4,7)1;

Adding 5*4=20 isosceles triangle and subtracting 2 (3,3,6) (3,3,7) is invalid; There are five equilateral triangles; A * * * has 9+ 18+5=32.