We want to take inventory of the right and left side
Right: S=1 O = 2 Li = 2 Se= 1
Left: S= 1 Se=2 Li= 2 O=1
Lets balance out each side because we see we are off by 1 oxygen on the left
Add a coefficient of 2 on the Li2O
Add a coefficient of 2 on the right Li2Se
Now we have So2+ 2Li2Se ---> SSe2+ 2Li2O
or
The equation is already balanced, assuming that there is supposed to be a yields symbol between 2Li2Se and SSe2.
To find out whether or not this equation is balanced, make a little T-chart with the left side of the equation on one side and the left on the other. Next to each element, write down the amount they start off with and make changes as you add coefficients.
Hope this helps!