Ammonium nitrate decomposes explosively to form nitrogen, oxygen, and water vapor.

There doesn't seem to be a question. I'm going to take a wild guess and say that what you want is a balanced equation.

Here is the unbalanced equation

NH4NO3(s) ===> N2(g) + O2(g) + H2O(g)  Start by balancing the N2 on the left

2NH4NO3(s) ===> N2(g) + O2(g) + H2O(g) Now balance the hydrogen

2NH4NO3(s) ===> N2(g) + O2(g) + 4H2O(g) You need 8 Hs

Go for the Oxygens.

They are balanced. There's 6 on the left and 4+2 on the right.