Zork goes running four days a week. His goal is to run a total of 25 miles. So far this week he has run 6.7, 4.5, and 7.0 miles. How far must he run on the fourth day?

6.8 miles

Step-by-step explanation:

First, find how far he has run this week. To do this, add together all his mileages so far.

6.7+4.5+7.0=18.2

So far, he has ran 18.2 miles.

He wants to run 25 miles, and has already ran 18.2 miles. The difference between the two will be how far he needs to run to reach his goal. Subtract 18.2 from 25

25-18.2=6.8

He will need to run 6.8 miles on the fourth day