_C6H8 + _O2 > _H2O + _CO2

C6H8+8O2 -> 4H2O + 6CO2

Explanation:

I first started with the carbons. On the left side we have 6 carbons, and on the left side only one, so I started by having 6CO2's on the right side. This then gave me 12O's to balance on the other side. I also realized that H2O only has 1 O which would be impossible to balance as it would mean an odd number of oxygens on the right and an even number on the left, so I made it 4H2O to also accommodate for the 8 hydrogens on the left side. Finally I added up the oxygens on the right (total of 16: 12 from the carbon dioxides and 4 from the water) and added an 8 to the oxygens on the left.

Hope this helped!