reprezint compusii: MClx si MBrx, unde M are masa A
(A+35,5x)g.MClx............A,gM
100g............................20,22g.....................>A/x= 9
(A+80x)gMBrx...........A,gM
100g........................10,11g.....................> A/x=9
daca x=1.....A=9
x=2....A= 18
x=3...A=27......> M este Al si are compusii AlCl3, AlBr3