Answer:
We are gonna called birds and dogs . So, if pet store had 10 more birds the number of dogs would be double, this means that:
In the expression we have 10 more birds , and the number of dogs is the double of these birds, which give us the expression.
So, the range of values would be:
If there are 10 birds, there would be 20 dogs.
If there are 11 birds, there would be 22 dogs.
If there are 12 birds, there would be 24 dogs, and so on...
13 birds, 26 dogs.
14 birds, 28 dogs.
All these results are given by the expression we found.