One-ninth of all sales at a local Subway is for cash. If cash sales for the week were $690, what were Subways total sales? This one is not clear. I know i am missing something here.

Let us assume the total sales of the local Subway = x

Then

Total sales done by cash at the local Subway = x/9

Total cash sales for the week at the local Subway = $690

Then

x/9 = 690

x = 690 * 9

= 6210 dollars

From the above deduction, it can be easily concluded that the total sales of the local Subway was $6210. I hope that the procedure is clear enough for you to understand.