Mario was visiting the carnival when he noticed a few number relationships.

If three tenths of the visitors were adults and there were 100 visitors that were adults?

There would be 30 adults because, if you were to take 3/10 and multiple both numbers until the denominator was 100 (10 X 10 = 100, 10 X 3 = 30). Resulting in your numerator to be 30. Therefore there were 30 adults.