Formula to measure percent of checklist complete

Hello,

I am trying to build a checklist where if you have completed the task on the list, you put an X in the cell below that task. As tasks are marked complete with the X, a cell at the end of the row containing the "X"s would add 1 to the sum. In other words, if I have added 5 X's to the list and there are 10 total, the cell at the end would have 5 in it. If I add an x to another completed task, it would change to 6 and if I delete an x it would go back to 5. Make sense? Thanks in advance.

My ultimate goal is to grab all the sum cells and figure a total % complete by combining several lists using this approach.