I believe it's A. Hope it helps :)
El mínimo común múltiplo de 20 14 y 17 es <u>1</u>.
17 es un número primo, y su únicos múltiplos son 17 y 1.
Aidan has put 21 hours of work. To simplify it, Harry worked 7 hours and Aidan worked 7 x 3 times which equates to 21 hours.
