Hi there!
∵ 1 mile = 1. 609344 km
∴ 1 kilometer =

miles
Then,
According to th' question :-
20 kilometers =

× 20 =

≈ 12. 4 miles.
FURTHER EXPLANATION :-
" Fibonacci's Sequence "
1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144...
Each term of the Fibonacci sequence is the sum of the previous two terms.
• "Golden ratio" ≈ 1.618 which's Quite close to 1.609344.
From sequence :-
find that 5 miles is about 8 kilometers, 21 kilometers is about 13 miles, etc.
Therefore,
In the case of 20 kilometers :-
20 = 21 -

= 12.4
~ Hope it helps!