Respuesta :

Answer:

18 trucks

Step-by-step explanation:

21 trucks every 28 hours

24 hours of 28 hours = 0.85714285714%

0.85714285714 x 21 = 18

or you can do

21 trucks every 28 hours =  3 trucks every 4 hours

4 hours x 6 = 24 hours

6 x 3 = 18 trucks