Look at the picture below and answer if you are able.

If you take 90 x 7/8 you get 78.75 min. That's how long he was doing flip tricks. To find the time he's been doing slides, you take the total time (90) minus the amount of flips (78.75) and you get 90-78.75 and the answer is 11.25. If this helped please hit the thanks button :)

So confused right here i need it to be more clearer