Answer:
There are 9 000 000 = 9 million reptiles in the US.
Step-by-step explanation:
Percentages and ratio:
The double of a measure, for example, is 200% of the measure.
So 1000% of a measure is 10 times the measure.
There are 90 million pet dogs in the US. The number of dogs is 1000% the number of reptiles.
The number of pet dogs is 10 times the number of reptiles, which means that:
There are 9 000 000 = 9 million reptiles in the US.