Can someone help me with this question

Pls brainliest will be awarded if answer is correct

Renee hiked for 6 3 /4 miles. after resting, renee hiked back along the same route for 5 1 /4 miles. how many more miles does renee need to hike to return to the place where she started? represent your answer as a simplified mixed number, if necessary.

Since we have computer algebra systems that can solve polynomial division problems for us, why is it necessary to learn how to do these things by hand?