The cup was tossed 50 times
This is the 100% of times it was tossed.
It landed 11 times right side up
14 times upside down
25 times on its side
To calculate the percentage that the times it landed on its side represent, you can use cross multiplication
50 times ____ 100%
25 time _____ x%
50% of the times the cup landed on its side