Here is your answer
C3H8 + O2-----> CO2 + H2O
Balancing C atoms
C3H8 + O2------> 3CO2 + H2O
Balancing H atoms
C3H8 + O2------> 3CO2 + 4H2O
Balancing O atoms
C3H8 +[tex]\bold{5}[/tex]O2-------> [tex]\bold{3}[/tex]CO2 + [tex]\bold{4}[/tex]H2O
Hence the equation is balanced.
HOPE IT IS USEFUL