The number of baseball cards he has is 9.
Ratio expresses the relationship between two or more numbers. It shows the frequency of the number of times that one value is contained within other value(s).
Number of baseball cards = (ratio of baseball cards / sum of ratios) x number of sport cards
(1/8) x 72 = 9 cards
To learn more about ratios, please check: https://brainly.com/question/25927869