To find out what percentage of Mr. Henderson's earnings he spends on food, we can use the formula for percentage:
\[ \text{Percentage} = \left( \frac{\text{Amount spent}}{\text{Total earnings}} \right) \times 100 \]
In this case:
- Amount spent on food = $80
- Total earnings = $800
Now we can calculate the percentage:
\[ \text{Percentage} = \left( \frac{80}{800} \right) \times 100 = 0.1 \times 100 = 10% \]
So, Mr. Henderson spends 10% of his earnings on food.