0620/12 Chemistry Oct Nov 2013 Online Test | Cambridge IGCSE MCQ

The chemical compositions of two substances, W and X, are given.
W $Na\left( {AlS{i_3}} \right){O_8}$
X $Ca\left( {A{l_2}S{i_2}} \right){O_8}$
Which statements are correct?
1 W and X contain the same amount of oxygen.
2 W contains three times as much silicon as X.
3 X contains twice as much aluminium as W.