11. Suppose you get a job selling Tshirts at a concert. You get $2 for each Tshirt you sell, but it costs you $5 to get into the concert. Let x represent the number of Tshirts you sell, and express the amount of money you will get out of this deal as a function of x. How many Tshirts will you have to sell to come home with $25?
Let x = the number of Tshirts you sell. Since each Tshirt brings in $2, you multiply the number of Tshirts by $2 to get the money from the sale of the Tshirts. This gives us
But out of these proceeds must come the $5 you had to spend to get into the concert. So we subtract 5 from the 2x and get
If the amount of money you need is $25, we get
Add 5 to both sides
2x 
 
5 
= 

25 

+ 
5 

+ 
5 
2x 


= 

30 
Divide both sides by 2
You would need to sell 15 Tshirts to come home with $25.
Check: If you sold 15 Tshirts you could get $30 from the sale of the Tshirts, so that when you took off the $5 you needed to get into the concert, you would be left with $25.