This equation C5H + O2 ---> CO2 + H2O has a mistake.
C5H is wrong. You missed the subscript of H.
I will do it for you assuming some subscript to show you the procedure, but you have to use the right equation to get the right balanced equation.
Assuming the tha combustion equation is C5H12 + O2 ---> CO2 + H2O
First you need to balance C, so you put a 5 before CO2 and get
C5H12 + O2 ---> 5CO2 + H2O
Now you count the hydrogens: 12 on the left and 2 on the right. So put a 6 before H2O and get:
C5H12 + O2 ---> 5CO2 + 6H2O
Now count the oxygens: 2 on the left and 16 on the right, so put an 8 on before O2:
=> C5H12 + 8O2 ---> 5CO2 + 6H2O.
You can verify that the equation is balanced