Oliva can take out 15 different pairs of dog.
Combinations are the way of selecting the objects or numbers from a group of objects or collection, in such a way that the order of the objects does not matter.
Since, Oliva has 6 dogs. and She walk two at time.
Number of different pairs of dogs = [tex]^{6}C_{2}[/tex]
[tex]^{6}C_{2}=\frac{6!}{2!*4!} =\frac{6*5*4!}{2*4!}=15[/tex]
Therefore, Oliva can take out 15 different pairs of dog.
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