Answer:
see the explanation
Step-by-step explanation:
Let
x ----> number of tennis balls
y ----> number of tennis rackets
we know that
To find out the ratio of tennis balls to tennis rackets, divide the number of tennis ball by the number of tennis rackets
In this problem we have

see the model in the attached figure N 1
so


This is the equation of a linear direct variation
The relationship between the variables x and y is proportional
see the model in the attached figure N 2