There are two alcohol solutions, the concentration of solution A is 75%, the concentration of solution B is 15%, now these two solutions are mixed to make 18 liters of alcohol solution with a concentration of 50%, how many liters of solution A should be taken.
有两种酒精溶液，甲溶液的浓度是75%，乙溶液的浓度是15%，现在要将这两种溶液混合成浓度是50%的酒精溶液18升，应取甲溶液多少升．
<gadget id="calculator">0.75 - 0.15</gadget>
<output>0.6</output>

<gadget id="calculator">6.3 / 0.6</gadget>
<output>10.5</output>

<result>10.5</result>