There are 330 grams of brine with a concentration of 4% in container A, and 120 grams of brine with a concentration of 7% in container B. Pour 180 grams from A to B. What is the concentration of brine in container B?
A容器中有浓度4%的盐水330克，B容器中有浓度7%的盐水120克，从A倒180克到B，B容器中盐水浓度是多少？
<gadget id="calculator">4 / 100</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">180 * (1/25)</gadget>
<output>36/5 = around 7.2</output>

<gadget id="calculator">7 / 100</gadget>
<output>7/100 = around 0.07</output>

<gadget id="calculator">120 * (7/100)</gadget>
<output>42/5 = around 8.4</output>

<gadget id="calculator">(36/5) + (42/5)</gadget>
<output>78/5 = around 15.6</output>

<gadget id="calculator">180 + 120</gadget>
<output>300</output>

<gadget id="calculator">(78/5) / 300</gadget>
<output>13/250 = around 0.052</output>

<result>13/250 = around 0.052</result>