5 kilometers.
1 kilometer is 1,000 meters, so 7 kilometers is 7,000 meters. 7,000-2,000=5,000 meters. Then move the decimal point to the left 3 times, to convert it back to kilometers. 5 kilometers.
An alternative is to make the meters into kilometers beforehand. So move the decimal point in 2,000 meters three times to the left to get 2 kilometers. Then subtract 2 kilometers from 7 kilometers to get 5 kilometers.
