Answer: There were 99 more skateboarders than skaters at the park on Saturday.
Explanation:
Let there were 8x skaters and 3x skateboarders on Friday.
There were 168 skaters on Friday.
So,


3x = 3 (21)=63
Total skaters and skateboarders on Friday = 168+63 = 231
Also, the ratio of the number of skaters to the number of skateboarders was 2:5
Let there were 2x skaters and 5x skateboarders on Saturday.
Then,


Number of skaters = 2(33) = 66
Number of skateboarders = 5(33) = 165
Difference = 165-66= 99
Hence, there were 99 more skateboarders than skaters at the park on Saturday.