Alexia ran three laps around her neighborhood. each lap is 1 3/8 miles. which is the best estimate of the number of miles that alexia ran
2 miles
4 1/2miles
3 1/2miles
6 miles

1 3/8 is equal to the improper fraction 11/8. When you multiply that by 3 (or 3/1), you get 33/8. To simplify this, think that 8 goes into 33 4 times, with a remainder of 1. So 33/8=4 1/8. This is closest to the answer 4 1/2 miles.

Each lap is 1 and 3/8 miles. 
She ran 3 miles.

1 mile * 3 = 3 miles
3/8 miles * 3 = 9/8 miles = 1 1/8 mile (remember 8/8 miles = 1 mile)

3 miles + 1 mile + 1/8 mile = 4 1/8 miles
Now the question is what estimate was the best:

Remember that 1/2 = 2/4 = 4/8 etc. 

The distance from 4 1/2 to 4 1/8 = 4 4/8 - 4 1/8 = 3/8 miles
The distance from 4 1/8 to 3 1/2 = 4 1/8 - 3 4/8 = 5/8 miles

As you can see, 4 1/2 was the closest estimate.

Hope this was of help :)