Jonah and his brother want to earn at least $400 this month, so they rented a lawn mower to mow lawns. They plan to charge $25 per lawn. The monthly rental fee for the lawn mower is $85. At this rate, what is the fewest number of lawns Jonah and his brother would have to cut to make their goal?
First, we must calculate the amount of money Jonah and his brother earn per lawn mowed by subtracting the rental fee from the amount charged: $25 - $85 = -$60
Per lawn, Jonah and his brother would actually lose $60.
To find the number of lawns they would have to mow, we divide the money they need to make by the amount they lose per lawn: $400 / -$60 = -6.666....
To have a positive answer, we round up to the nearest whole lawn, meaning they would have to mow 7 lawns. Answer: \boxed{7}.