What have you tried? You will need to have the values for Tacoma, Bellevue, Ontario and LA available at a higher level of aggregation. See the example created in the attached 10.3 packaged workbook where I have replaced the value of Sales for Tacoma with Bellevue sales/Tacoma Sales - and all of the rest of the rows display sales for their cities.
This method should work for the calculations you would like to do.
I hope that helps.