Meimei Department Store bought a batch of gloves at the wholesale price of 6.5 yuan per pair, and the retail price of 9 yuan per pair. When there were 50 pairs of gloves left after the sale, the calculated money earned 100 yuan in addition to the cost of all the gloves ． How many pairs of gloves has the store sold?
美美百货商店按批发价购进一批手套，每双6.5元，零售价每双9元，当卖出还剩50双手套时，计算所得的钱除去全部手套的成本外，已获利100元．商店已卖出多少双手套？
<gadget id="calculator">9 * 50</gadget>
<output>450</output>

<gadget id="calculator">450 + 100</gadget>
<output>550</output>

<gadget id="calculator">9 - 6.5</gadget>
<output>2.5</output>

<gadget id="calculator">550 / 2.5</gadget>
<output>220</output>

<gadget id="calculator">220 - 50</gadget>
<output>170</output>

<result>170</result>