Sam and Sylvia work at a bookstore. Sam sold 15% more books than Sylvia. If Sam sold 69 books how many did Sylvia sell?

lets take

X= Number of books that sylvia sold = 100%

Now, Sam's sold 15% more books than sylvia which makes it that sam's sold (100%+15%) =115%

when taking % off( simply you devide by 100-----> 115/100 =1.15) that amount of books sold by Sam's =1.15X

1.15x=69 books

X=60= number of books sold by Sylvia.