Answer:
Katie will have left $7 with her after donating to 7 charities.
Explanation:
Katye received 15 gifts and a total of $100 in cash for her birthday. 
She buys one book that costs $23, and she wants to donate $10 to each of several local charities. 
After buying a book, amount left with her = 
 dollars
As she wants to donate $10 to each charity, that means she can donate to 
 rounded to 7 charities.
She will have left 
 dollars
So, Katie will have left $7 with her after donating to 7 charities.