Answer:
equation: 35 + 20w = 155
w = 6
He needs $155, and he already has 35. The 20 is how much he will get a week, and the w represents how many weeks will pass before he gets enough twenties for the shoes.
If he gets $20 each week, and he already has $35, then after 6 weeks he will have enough money for the shoes.
hope this helps