[질문] 방정식 x+y+z=7 의양의정수해의개수는?

13개 입니다. (1,1,5) (1,2,4) (1,3,3) (1,4,2) (1,5,1) (2,1,4) (2,2,3) (2,3,2) (2,4,1) (3,1,3) (3,2,2) (4,1,2) (4,2,1)