A shopping mall buys milk powder, buys 5 bags for 15 yuan, sells 3 bags for 15 yuan, and wants to make a profit of 90 yuan, how many bags need to be sold.
某商场进奶粉，进货5袋15元，卖出3袋15元，要获利90元，需要卖出多少袋．
<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">90 / 2</gadget>
<output>45</output>

<result>45</result>