1/4 of 80 men is 80/4=<<80/4=20>>20 men
20 men couldn't finish, so 80-20=<<80-20=60>>60 men remain
60*2/3 = <<60*2/3=40>>40 men were dehydrated
1/5 of the dehydrated couldn't finish 40*1/5=<<40*1/5=8>>8 men
60-8=<<60-8=52>>52 men finished the race
#### 52