Answer:
891 miles
Step-by-step explanation:
You can either multply 81*11 or add 81 to itself 11 times
1 week: 81 miles
2 weeks: 81+81=162 miles
3 weeks: 162+81=243 miles
4 weeks: 243+81=324 miles
5 weeks: 324+81=405 miles
6 weeks: 405+81=486 miles
7 weeks: 486+81=567 miles
8 weeks: 567+81=648 miles
9 weeks: 648+81=729 miles
10 weeks: 729+81=810 miles
11 weeks: 810+81=891 miles
