Lynne ran farther and by 7/8 miles
You can tell Lynne ran further because she ran 3 whole miles while shelly only ran 2 whole miles. Now you have to subtract to see how much Lynne had ran more.
You found a common denominator between 8 and 4. 4 can turn into 8. so you multiply 4x2 and 1x2 to get a mixed number of 2 2/8
Now you have to turn 3 1/8 because you cannot subtract 2/8 from 1/8. You can turn the fraction into 2 9/8 because there are 8 pieces in a whole.
2 9/8 - 2 2/8 = 0 7/8
Hope this helps! :)
