# What coefficient is placed in front of O_2 to complete the balancing of the following equation C_5H_8 + ?O_2 -> 5CO_2 + 4H_2O?

${C}_{5} {H}_{8} + 7 {O}_{2} \to 5 C {O}_{2} + 4 {H}_{2} O$
The coefficient for ${O}_{2}$ is 7.
${C}_{5} {H}_{8} + 7 {O}_{2} \to 5 C {O}_{2} + 4 {H}_{2} O$