Answer: it takes her 6 weeks to save $180
Explanation:
Kristen has been earning $150 per week by babysitting. This means she earns a total of $150 every week for babysitting. She has been working to save 20 percent of each weeks earning. This means she saves 20/100 × the amount she earns every week.
She saves 20/100× 150
= 0.2 × 150 = $30
She continues to save this amount in order to save a total of $180.
Number of weeks it will take her to save $180
= total amount / amount saved in a week
= 180 / 30 = 6 weeks