Answer:
She drives 253 miles each week.
Explanation:
She lives 8 miles from the office.
For each of 5 days during the week, she drives 8 miles to the office and 8 back home. So for each day, 8 + 8 = 16 miles
On Saturday, she drives 173 miles to visit her sister(Since it is not expressed, 173 miles counts both the drive from her home to her sister and the drive back).
In total:
5*16 + 173 = 253
She drives 253 miles each week.