You have probably scanned the worksheet as a picture.

You cannot "work on" a picture.

What you need is a good OCR application with your scanner which allows you to
scan as Text file output.

Then copy/paste to a sheet or open directly in Excel.

Depending upon your OCR application's efficency, you won't have too much editing
to do, although  numbers will come in as text and will have to be changed to
real numbers.

Gord Dibben  MS Excel MVP