Hello!
First you have to list the miles he ran
He started with 1.75 and increases it by 0.25 miles every day
He ran 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, 4.75, 5, 5.25, 5.5, 5.75 and 6 miles
Now we add all these numbers
1.75 + 2 + 2.25 + 2.5 + 2.75 + 3 + 3.25 + 3.5 + 3.75 + 4 + 4.25 + 4.5 + 4.75 + 5 + 5.25 + 5.5 + 5.75 + 6 = 69.75
The answer is B) 69.75 mi
Hope this helps!