Frank wants to buy a new lamp for his bedroom. The cost of the cheapest lamp is $20, and the most expensive in the store is 3 times more expensive. How much money would Frank have remaining, if he currently has $90, and he buys the most expensive lamp available?
The most expensive lamp cost 20 * 3 = $<<20*3=60>>60.
So if Frank would pay for that lamp, he would leave himself with 90 - 60 = $<<90-60=30>>30.
#### 30