-7=-9+n/8
Add 9 to both sides
2=n/8
Multiply 8 on both sides
Final Answer: 16=n

Combine like terms and "plug in" x into the equation to eventually get 34 after some addition
Company 1 average= 24.4 minutes
company 2 average= 19.8 minutes
company 3 average= 15 minutes
company 4 average= 19 minutes
The answer is 24.4 or company one