I got the answer because if you multiply the number of feet that make up that one side of the tent, you get 40. However, you need the to find out the feet of the whole tent, and there are four sides of the tent, so you'd have to multiply 40 by four to get the total amount of feet for the whole tent which comes out to 160.
Each taco sells for $3, so t tacos will bring in 3t dollars. Each burrito sells for $5.25, so b burritos will bring in 5.25b dollars. Therefore, the total amount of revenue 3t+5.25b must be greater than or equal to $470: