B=number of brownies baked. 5B/9 given to cheerleaders leaving 4B/9 half of which (2B/9) went to football. That's a total of 5B/9+2B/9=7B/9 given out. 2B/9 remain and 2B/9=10, so 2B=90 and B=45.
CHECK: 5/9*45=25 to cheerleaders; 20 left, half of which went to football leaving 10. Correct!