Don, an office equipment sales representative, earns a weekly salary plus a commission on his sales. One week his total compensation on sales of $6000 was $600. The next week his total compensation on sales of $9000 was $690. Find don’s weekly salary and his commission rate

Answer 1

You have 2 equations you could be working with.
Firstly the form of the equations is
Earnings = Salary + (commission rate)x(sales)
In the first instance Don made
600 on 6000 in sales so
1) 600 = Salary + 6000x
on 9000 in sales he made $690
2) 690 = Salary + 9000x
If we re-arrange both for Salary we obtain
1) 600- 6000x = Salary
2) 690 - 9000x = Salary
By the "comparision method" since the right hand sides are equal we can set the left hand sides equal ... and solve for x
600- 6000x = 690 - 9000x
bring the x's to one side and the numbers to the other
- 6000x + 9000x = 690 - 600
3000x = 90
x = .03
So the commission rate is 3%
Now just sub that back into either equation 1) or 2) and solve for the salary : )