Shelby had $20 to take to the book fair. She bought one book for $8 and another for $4. She decided to buy as many $4 posters as she could with the money she had left. How many posters can she buy?
She spent $8 + $4 = $<<8+4=12>>12 on books.
She started with $20, so she has $20 - $12 = $<<20-12=8>>8 left to spend on posters.
Each poster costs $4, so she can buy $8 / $4 = <<8/4=2>>2 posters.
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