11. Suppose you get a job selling T-shirts at a concert. You get $2 for each T-shirt you sell, but it costs you $5 to get into the concert. Let   x   represent the number of T-shirts you sell, and express the amount of money you will get out of this deal as a function of   x.   How many T-shirts will you have to sell to come home with $25?

Let   x =   the number of T-shirts you sell. Since each T-shirt brings in $2, you multiply the number of T-shirts by $2 to get the money from the sale of the T-shirts. This gives us

2x

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

2x - 5

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If the amount of money you need is $25, we get

2x - 5 = 25

Add 5 to both sides

2x

-

5

=

25

+

5

+

5

2x

=

30

Divide both sides by 2

x = 30/2

x = 15.

You would need to sell 15 T-shirts to come home with $25.

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Check: If you sold 15 T-shirts you could get $30 from the sale of the T-shirts, so that when you took off the $5 you needed to get into the concert, you would be left with $25.

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