Answer: If Shelly made 19 treat bags, and 11 of them were for girl guests, then the remaining bags were for boy guests.
So the number of boy guests = 19 - 11 = 8
Then the ratio of boy guests to girl guests is 8:11
or you can simplify it by dividing 8 and 11 by greatest common factor which is 8/11 in this case.
or you can express it as 8/19 for boy guests and 11/19 for girl guests
Explanation: