The ratio is children:adults = 8:1
You just need to increase each in a fraction form until the difference is obtained
For example: (8/1)*(25/25) = 200/25 Difference = 200 - 25 = 175 Not the answer
try (8/1)*(20/20) = 160/20 Difference = 160 - 20 = 140 Not the answer ... but close!
try (8/1)*(21/21) = 168/21 Difference = 168 - 21 = 147 YES... and 168/21 = 8/1
So Tickets sold were 168 Children & 21 Adults