Answer: it will take 6 weeks until she has enough money to buy the bike.
Explanation:
Let x represent the number of weeks until rachel has enough money to buy the bike.
She currently has $150 and is saving $10 each week. It means that the total amount that she would have saved after x weeks is
150 + 10x
The bike costs $300. The bike owner is decreasing the price of the bike $15 every week. It means that the cost of the bike after x weeks is
300 - 15x
For Rachel to save enough money to buy the bike, the number of weeks would be
300 - 15x = 150 + 10x
10x + 15x = 300 - 150
25x = 150
x = 150/25
x = 6