Calculating Production Quantities for equal Days on Hand

Having trouble with aligning a production schedule to produce the same number of days on hand [DOH] across three packaging types. A total of 480.3 units has to be produced across the three packaging types. All three packaging types have different inventory levels and daily rate of sales [DROS]. how do I solve for A, B, and C so that X = the same number of days:

Product Inventory DROS Breakdown DOH
Type A 193 9.19 a x
Type B 36 1.72 b x
Type C 17 0.81 c x


480.3