Arrange these lunch buyers from greatest to least assuming they buy lunch 5 days per week: Alice spends $3 per day, Betty spends $25 every 2 weeks, and Cindy spends $75 per month.

Alice spends $3 per day, so for in a week and upto 5 weeks, Alice spend = $3*5*5 = $75

Betty spends $ 25 every 2 weeks, so for 5 weeks, she spends = 25+25+12.5

= $62.5

Cindy spends $ 75 per month, and on an average there are less then 5 weeks in a month. SO for 5 week, it must be greater than $75.

So the order is

Cindy>Alice>Betty