Elijah's error lies in how he set up his equation to calculate the percentage.
To find the percentage of the race that is mountain biking, he should have set up the equation like this:
\[ \text{Percentage} = \left( \frac{\text{Part}}{\text{Whole}} \right) \times 100 \]
In Elijah's case, the "Part" is 8 miles (mountain biking) and the "Whole" is 26 miles (total race distance).
The correct setup should be:
\[ \text{Percentage} = \left( \frac{8}{26} \right) \times 100 \]
From the options given, the correct statement about Elijah's error is:
Elijah should have multiplied 8 by 100 and ? by 26.
This reflects the proper way to solve for the percentage, which is to multiply the part (8) by 100 and then divide by the whole (26).