The cycling part was 12 1/2 miles long.
Hence the distance covered by cycling is 12.5 miles
The running part of the race was 1/4 the distance of the cycling part.
The running part is 0.25 of the cycling part.
So running part = 0.25 × 12.5 = 3.125 miles
The kayaking part of the race was 1/2 the distance of the running part.
So kayaking part is 0.5 of the running part.
So kayaking part = 0.5 × 3.125 = 1.5625 miles
Hence the total distance
= 12.5 + 3.125 + 1.5625
=17.1875 miles
The entire distance in miles of the race is 17.1875 miles