A bottle of salt water, the ratio of salt to water is 1:5, then add 50 grams of salt, the ratio of salt to water is 1:4. How many grams of salt is in this bottle of brine?
一瓶盐水，盐与水的比是1：5，再加入50克盐，盐与水的比是1：4．原来这瓶盐水中有盐多少克？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">50 / (1/20)</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 * (1/5)</gadget>
<output>200</output>

<result>200</result>