24 g of methane burns completely: CH₄ + 2O₂ → CO₂ + 2H₂O…

Step 1. Moles. $\dfrac{24\ \text{g}}{16\ \text{g/mol}} = 1.5\ \text{mol}$ of methane.

Step 2. Oxygen. $3\ \text{mol} \times 32\ \text{g/mol} = 96\ \text{g}$.

Step 3. Carbon dioxide. $1.5\ \text{mol} \times 44\ \text{g/mol} = 66\ \text{g}$.

Step 4. Water. $3\ \text{mol} \times 18\ \text{g/mol} = 54\ \text{g}$.