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**m58** If $\displaystyle S$ is the set of positive integers that are multiples of $\displaystyle 7$, and if $\displaystyle T$ is the set of positive integers that are multiples of $\displaystyle 13$, how many integers are in the intersection of $\displaystyle S$ and $\displaystyle T$?

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?