Question

Sarah has run 108 miles over the last 15 days while preparing for an upcoming marathon. She ran either 6 miles a day or 8 miles a day. During the 15 day period, how many days did Sarah run an 8 mile day? A) 6 B) 7 C) 8 D) 9

Answer 1

D)
She ran 8 miles for 9 days and 6 miles for 6 days

8x9=72
6x6=36
72+36=108

Answer 2

Solution:

we are given that

Sarah has run 108 miles over the last 15 days while preparing for an upcoming marathon. She ran either 6 miles a day or 8 miles a day.

we have been asked to find

During the 15 day period, how many days did Sarah run an 8 mile day?

Let she ran 8 miles for x days, it mean she ran 6 miles one each of the (15-x) days. Then we can write

$8x+(15-x)6=108\\ \\ \text{we can simplify it as below}\\ \\ 8x+90-6x=108\\ \\ 2x=108-90\\ \\ 2x=18\\ \\ x=9$

Sarah run an 8 mile day for 9 days.