lift to drag = 12:1, assume lift = 12 bananas, drag = 1 banana, where a banana is an arbitrary unit.
thrust to weight = 1:4, assume thrust is 3 bananas and weight 12 bananas (this done so that lift= weight, which is what the question assumes)
If this is the case the (Thrust - Drag) ÷ weight = (3 bananas - 1 banana) ÷ 12 bananas = 2/12 or 1/6.
1/6 = 0.16666 recurring