A survey conducted by the school showed that only 20% of the 800 parents agree to a tuition fee increase. How many parents disagree with the tuition fee increase?
There were 800 x 20/100 = <<800*20/100=160>>160 parents who agreed to the tuition fee increase.
So, there were 800 - 160 = <<800-160=640>>640 parents who disagreed.
#### 640