Answer: There are 12 pairs of tennis shoes.
Explanation:
Since we have given that
For each pair of tennis shoes , she owns 4 pairs of flip flops,
so their ratio will be 1:4
Let the number of tennis shoes be x
Let the number of flip flops be 4x
According to question,
4x-x=9
3x=9
x=\frac{9}{3}
x=3
So, the number of pairs of tennis shoes is given by

Hence, there are 12 pairs of tennis shoes.