Can you keep the mole ratio the right way round?

Ammonia decomposes: $2\mathrm{NH_3} \rightarrow \mathrm{N_2} + 3\mathrm{H_2}$. Calculate the mass of hydrogen made from $25.0\,\mathrm{g}$ of ammonia. $M_r(\mathrm{NH_3}) = 17$ and $M_r(\mathrm{H_2}) = 2$.