4:1 means for every four soccer player there is 1 volleyball player
that means there are four times the number of soccer players than volleyball players
We know all the side lengths so can use law of cosines. a=90, b=55, and c=50.
2500=8100+3025-2(90)(55)cos(C)
cos(C)=.8712
C=arccos(.8712)=29.4 degrees