Answer:
7 miles
Explanation:
If Juan's mother drives him 2/3 of the way to work, then he has to walk 1- 2/3 = 1/3 of the way to work.
To calculate the distance Juan has to walk, we need to multiply the total distance by 1/3:
distance to walk = total distance × 1/3
distance to walk = 21 miles × 1/3
distance to walk = 7 miles
Therefore, Juan has to walk 7 miles to get to work.