Let's use the variable x to represent the sales in a week.
In the first company, the total payment is 3% of x, that is, 0.03x
In the second company, the total payment is $260 plus 2% of x, that is, 260 + 0.02x.
The value of x that makes both options be equally good (same payment) is:
Therefore the sales should be $26,000.