Answer
$C_3H_8+5O_2\rightarrow 3CO_2+4H_2O$
Work Step by Step
$C_3H_8+O_2\rightarrow CO_2+H_2O$
Use a coefficient of 3 for $CO_2$ to balance $C$.
Use a coefficient of 4 for $H_2O$ to balance $H$.
$C_3H_8+O_2\rightarrow 3CO_2+4H_2O$
Use a coefficient of 5 for $O_2$ to balance $O$.
$C_3H_8+5O_2\rightarrow 3CO_2+4H_2O$
