Molly runs each morning once around a circular path in her neighborhood. if the diameter of the path is 1.4 miles, how far does molly run each day?

To work out the distance of the path, you need to find out the circumference.
Formula for circumference = pi multiplied by the diameter

So you simply do:
pi multiplied by 1.4 miles

And you should get:
4.39822971503... miles

Simply round the result to an appropriate value (e.g. 3 decimal places).

4.398 miles (to 3dp)
Hope the answer helps :)