Answer:
9/12 (or 3/4)
Step-by-step explanation:
If you subtract the number of brownies that Brittany's brother will eat, you will have 9 remaining brownies. So, that means 9 out of the original 12 brownies will be left, or 9/12. Also, you can simplify the fraction. Both 9 and 12 can be divided by 3.
9/12 divided by 3/3 equals 3/4. 3/4 is the fraction in it's simplest form.
So, 9/12 (or 3/4) of the brownies are left.
I hope this helps! Have a lovely day!! :)
