What is this question asking you to do?
(1) figure out how many miles the girls ran, then
(2) convert those miles to kilometers.
If 1 lap is 1/4 mile, then 4 laps is 1 mile.
If the girls ran 4 more laps than the boys' 16 laps, they ran 20 laps.
How many miles is that? 20 ÷ 5 = 4
Take your 4 miles and convert them to kilometers.
1 mile = 1.60934 km
4 miles = 4 x 1.60934 km
Your answer is 6.43736 km