How can I adjust the equation on the bottom to solve for all parts?

example: how to find Total quantity, To-date quantity, allowed credit?

Allowed Subtask Total Credit U/M .20 Delivery % .25 Columns Each .40 Beams Each .10 Plumb .05 Punchlist % 1.00 Steel Erection Tons 400 Total Number of Tons: Total To-Date Earned Quantity Quantity Tons 100 100 80 80 80 100 200 100 80 100 20 100 0 0 280 % 50 QTD x Allowed Credit x Total Tons = ET T