设有永生金笔X支(143-X)×3.78=540.54-3.78X应付款的总数与永生金笔的总数无关,所以付款总数为540.54元设卖出的永生金笔占总数Y6XY-3.78X=(6Y-3.78)X因为应付款的总数与永生金笔的总数无关,所以(6Y-3.78)X=0即6Y=3.78Y=0.63Y=63%