Respuesta :

17) he rented the bike for six hours.

19) he either has 50 poster if you include the six
or 44
17 - $49 - $19 = 30
        $30/ $5 per hour = 6 hours
 
Darryl rented the bike for 6 hours

18 - If there are 22 posters left, and half of them burned, so that means that originally there were double of 22 which is 44.
So he had 44 originally but bought 6 more and we have to double the six so that's 44 + 12 = 56

Adam had 56 posters to start with

Your answer is: Darryl- 6 hours; Adam- 56 posters 

Have an amazing day!