If is the set of positive integers that are multiples of , and if is the set of positive integers that are multiples of , how many integers are in the intersection of and ?

I said there is 1 integer in the intersection, since only 91 is a common multiple of 7 and 13. However, according to the answer,

91's multiples include 186, 278, etc, so I'm guessing the infinity is referring to that. However, I thought the problem only wanted an integer that was only multiple of 7 and 13?This is the set of all positive integers that are multiples of . There are an infinite number of positive integers that are multiples of , so there are more than thirteen integers in the intersection of and .