Make the equation equal on each side.
With number 1 it says the left side of the arrow has 1 Sn, 2 S, and 2 O.
The right has 1 Sn, 4 O, and 1 S.
So you have to balance the equation by putting numbers in front of the compounds.
SnS2 + O2 = SnO2 + SO2
SnS2 + 3 O2 = SnO2 + 2 SO2
Now there is 1 Sn, 2 S. and 6 O on each side. The large number in front of the compounds essentially multiplies it by that the subscript of that number. So with O2 it says there are 2 Oxygens. So they come in pairs. If you get 3 pairs of Oxygens there will be 6.
The same process goes with the rest of them too. Sometimes it takes a few guesses. Just figure them out like an algebra problem. Put the equal sign between them like I did. It maked it easier for me.
