How do these equations explain why the total amount of O2 and CO2 remains the same?

Chemical reactions is defined as the reaction between one or more reactants to form a product(s). Photosynthesis and aerobic respiration is a type of chemical reaction in which input of carbon dioxide is same as output of oxygen.
Photosynthesis is a chemical process in which carbon dioxide, water, and sunlight react to form glucose and release oxygen. The oxygen released by plants are utilised by animals for aerobic respiration.
The total amount of oxygen and carbon dioxide remains same as:
[tex]\begin{aligned }\text {photosynthesis} \;- 6\text{CO}_{2} + 6 \text {H}_{2}\text{O} +\text {light}\rightarrow\; \text{C}_{6}{\text H}_{12}{\text O}_{6}+6 {\text {O}}_{2}\\\text {respiration}\;- \text{C}_{6}{\text H}_{12}{\text O}_{6}+6 {\text {CO}}_{2} + 6\text{CO}_{2}\rightarrow\; 6 {\text {O}}_{2}+ 6 \text {H}_{2}\text{O} + \text {energy}\\\end {aligned}[/tex]
[tex]\text{C}_{6}{\text H}_{12}{\text O}_{6} +6\text{CO}_{2}+ 6 {\text {O}}_{2}+6 \text {H}_{2}\text{O}+\text{light}\rightarrow\;\text {C}_{6}{\text H}_{12}{\text O}_{2}+{\text O}_{2}+6\text{CO}_{2}+6 \text {H}_{2}\text{O} +\text {energy}[/tex]
Therefore, from the above equation, stoichiometrically, the amount of oxygen and carbon di oxide will remain same.
To know more about balancing chemical equation, refer to the following link:
https://brainly.com/question/12387201?referrer=searchResults