Explanation:
We'll let y represent the remaining money, x represent the number of weeks, and 30 represent the amount she spends per week. So, we have: y = 400 - 30x. To determine how much money she'll have left after 5 weeks, we just plug in 5 for x: y = 400 - 30(5) = 400 - 150 = 250. So, after 5 weeks, she'll have $250 left. To determine how many weeks it will take for her to have $10 left, we need to solve the equation for when y = 10. We can do this