Finding a Target Number

I need a formula and I am not sure if I am describing this right or not. This place has 4 weeks to hit this target number. How can I find exactly what number they need to hit to hit their target.

Place: Week 1 Week 2 Week 3 Week 4 Target #
XX 9.61% 6.65% 7.74% need to know (they need to hit 6.5% with all 4 numbers combined)


what kind of formula would I use?

Hello PaulB and Welcome to Excel Forum.
This appears to be more of a math problem than an Excel problem.
Target = (Week1 + Week2 + Week3 + Week4)/4 so;
6.5 = (9.61 + 6.65 + 7.74 + Week4)/4 so;
4 x 6.5 = 9.61 + 6.65 + 7.74 + Week4 so;
26 = 9.61 + 6.65 + 7.74 + Week4 so;
26 - 9.61 - 6.65 - 7.74 = Week4 therefore;
2 = Week4
If the values of weeks 1, 2 and 3 are known then you could use the following formula to find the value of week 4:
4 x Target - value week1 - value week2 - value week3 = value week4
It would help to see the spreadsheet set up before trying to be more specific.
To attach a sample workbook click on the GO ADVANCED button below the Quick Reply window and then scroll down to Manage Attachments to open the upload window.
Let us know if you have any questions.

It would be easier to help if you could upload the spreadsheet from which the screen shot in post # 6 is taken, as per the directions in post #3. For one thing I can't tell if "Store #" is in cell A1 or C10 so it makes it hard to write a formula(s).
That said, assuming "Store#" is in A1, the formula for week 4 it would be: = 4*B7 - B2 - B3 - B4
or
= 4*B7 - SUM(B2:B4)
Let us know if you have any questions.