Venn Diagram is attached below
In the diagram,x represents the player who likes both Chemstrand and Chemgrass. That is the intersection part in the venn diagram. So the value of x is 13.
y represents the player who likes Chemgrass but doesnot like Chemstrand . That is Chemgrass alone in the venn diagram. So the value of y is 17.
z represents the player who likes Chemstrand but doesnot like Chemgrass. That is Chemstrand alone in the venn diagram. So the value of z is 15.
Therefore, x=13, y=17 and z=15