There are two bottles of salt water in bottle A and bottle B. The concentration of the salt water in bottle A is three times that of the salt water in bottle B. Mix 100 grams of salt water in bottle A and 300 grams of salt water in bottle B to obtain a new salt water with a concentration of 15%. What is the concentration of the salt water in bottle A?
甲乙两瓶盐水，甲瓶盐水的浓度是乙瓶盐水的3倍，将100克甲瓶盐水与300克乙瓶盐水混合后得到浓度为15%的新盐水，那么甲瓶盐水的浓度是多少？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">100 * (3/20)</gadget>
<output>15</output>

<gadget id="calculator">300 * (3/20)</gadget>
<output>45</output>

<gadget id="calculator">15 + 45</gadget>
<output>60</output>

<gadget id="calculator">100 * 3</gadget>
<output>300</output>

<gadget id="calculator">300 + 300</gadget>
<output>600</output>

<gadget id="calculator">60 / 600</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">3 * (1/10)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>