Joe worked in a shoe department where he earned $325 weekly and 6.5% commission on all of his sales.

[math_celebrity]

Joe worked in a shoe department where he earned $325 weekly and 6.5% commission on all of his sales. What was joe’s total sales if he earned $507 last week

Let s be total Sales. 6.5% is 0.065 as a decimal, so Joe's earnings are given by:
0.065s + 325 = 507

To solve for s, we type this equation into our math engine and we get:
s = 2800