At the cubs/white sox baseball game on sunday night, 65% of the fans were men. another 25% were women. of the remainder, 40% were boys and the rest were girls. if 640 boys attended the game, what was the total number of people in attendance?

There were 16,000 people in attendance.

65% were men and 25% were women; that leaves 10% of the people in attendance.  Of this 10%, 40% of them were boys, and there were 640 boys; this gives us 0.1(0.4)x = 640:
0.04x = 640

Divide both sides by 0.04:
0.04x/0.04 = 640/0.04
x = 16000