Good night

Let n be an odd integer >=5.

1) Find the number of pairs (x,y) of positive integers which satisfy the equation x+2y=n.

2) Find the number of triples (x,y,z) of positive integers which satisfy the equation x+y+2z=n.

1) the answer is (n-1)/2

I put x+2y=n

y = (n-x)/2

the n is odd then n= 2k + 1 and x+2y=n then x = 1

y = (n-1)/2

???

2) the answer is [(n-1)(n-3)]/4