Find the sum, then divide by 3 to find the average.

• Convert all to decimals: 12 + 11.8 + 8.5 = 32.3 km
• Average = 32.3 ÷ 3 = \( \frac{323}{30} \) km
• \( \frac{323}{30} = 10\frac{23}{30} \) (since 323 ÷ 30 = 10 remainder 23)

Check: \( 10\frac{23}{30} \times 3 = \frac{323}{30} \times 3 = \frac{323}{10} = 32.3 \). ✓

Final Answer: \( 10\frac{23}{30} \) km