Draw a diagram of given problem.
Find translational velocity after the sphere starts pure rolling.
As we know, angular momentum is conserved about lowest point.
Therefore,
mv0r+25mr2v02r=mv′r+25mr2v′r
10mv0r+2mv0r10=7mv′r5
v′=6v07
Hence, we get
x=6 and y=7
i.e., (x+y)=6+7=13