Here's how to write the balanced chemical equation for the combustion of methylcyclononane:

1. Identify the Reactants:

* Methylcyclononane: C₁₀H₂₀ (a hydrocarbon)

* Oxygen: O₂ (the oxidant)

2. Identify the Products:

* Carbon Dioxide: CO₂

* Water: H₂O

3. Write the Unbalanced Equation:

C₁₀H₂₀ + O₂ → CO₂ + H₂O

4. Balance the Equation:

* Carbon (C): There are 10 carbon atoms on the left and only 1 on the right. Put a 10 in front of CO₂.

* Hydrogen (H): There are 20 hydrogen atoms on the left and only 2 on the right. Put a 10 in front of H₂O.

* Oxygen (O): There are 2 oxygen atoms on the left and 30 on the right (20 from CO₂ and 10 from H₂O). Put a 15 in front of O₂.

5. The Balanced Chemical Equation:

C₁₀H₂₀ + 15O₂ → 10CO₂ + 10H₂O