no. of moles of X=5/60=1/12.
since X,Y and Z must be in 1:2:3 ratio,the limiting reagent is Z
and thus 1/100 moles of the compound is formed which is given as 4.4 gms.
hence mol wt of compund is 4.4 X100=440.
let the atomic wt of Y be some m.
we get atomic wt of Y,m=70.