The answer is 143 miles.
EXPLANATION
The ratio between Dory's miles and Karly's miles is 11:1. This means that we need to divide 156 by 12, which is 13.
Because Dory's miles make up 11/12 of the total miles, we need to take 1/12 (which is 13) from the 156 to get the final answer of 143 miles.
