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Answer:
If our random variable of interest for this case is X="the number of teenagers between 12-17 with smartphone" we can model the variable with this distribution:

And the mean for this case would be:

And the standard deviation would be given by:

Step-by-step explanation:
If our random variable of interest for this case is X="the number of teenagers between 12-17 with smartphone" we can model the variable with this distribution:

And the mean for this case would be:

And the standard deviation would be given by:

Answer:
4.5=4 and 1/2
Step-by-step explanation: