Hello, Jaden,
I'll assume this is a decomposition reaction. We need to have a balanced equation as the first step.
I arrive at:
NH4NO3 = N2O + 2H2O [Use caution storing this compound. If part starts decomposing, the released energy will set off the rest].
Next, convert 24.6 grams of ammonium nitrate into moles NH4NO3.
(24.6 g)/(80.0 g/mole) = 0.308 moles NH4NO3
The balanced equation promises 1 mole of N2O for every 1 mole of NH4NO3, a molar ratio of 1:1. This means we should expect 0.308 moles of N2O.
Convert moles N2O into grams by multiplying times the molar mass of N2O:
(0.308 moles)*(44.0 g/mole) = 13.6 g N2O
Bob