\(M_{MgSO_4}=24+32+16.4=120\\ \%Mg=\dfrac{24}{120}.100=20\%\\ \%S=\dfrac{32}{120}.100=26,67\%\\ \%O=\dfrac{16.4}{120}.100=53,33\%\\ M_{Al\left(NO_3\right)_3}=27+62.3=213\\ \%Al=\dfrac{27}{213}.100=12,68\%\\ \%N=\dfrac{14.3}{213}.100=19,72\%\\ \%O=\dfrac{16.9}{213}.100=67,6\%\)