Alfonso earns $6 each day walking his aunt’s dog. He is saving to buy a mountain bike helmet for $340. Currently, he already has $40. If he walks his aunt's dog 5 days a week, in how many weeks should Alfonso work to buy his mountain bike?
Alfonso has to work for the $340 - $40 = $300.
In a week, he earns $6 x 5 = $30.
Thus, he needs to work $300/$30 = 10 weeks to buy the bike.