Respuesta :

articunojaz
The reactants has 2 NO2 and the product has 3. So we need to make sure we have 6 on each side. 
Al + 3Fe(NO2)2 -> Fe + 2Al(NO2)3 
This leaves us with us just to balance the Fe And Al 
2Al + 3Fe(NO2)2 -> 3Fe + 2Al(NO2)3

Hope this helped :)