The two brothers jointly invested 5 million yuan in the joint venture, and later the younger brother added an additional investment of 200,000 yuan. At this time, the elder brother's investment amount is exactly three times that of the younger brother's investment amount. Then how many million yuan did my brother invest.
兄弟两人共同投资500万元合办企业，后来弟弟又追加20万元投资额．这时，哥哥的投资额恰好是弟弟投资额的3倍．则哥哥投资了多少万元．
<gadget id="calculator">500 + 20</gadget>
<output>520</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">520 / 4</gadget>
<output>130</output>

<gadget id="calculator">130 * 3</gadget>
<output>390</output>

<result>390</result>