Put a drink in an empty water jug, pour 2 cups of drink into the jug and weigh 90 grams in total, and pour 5 cups of drink into the jug and the weight of the jug is 138 grams. How many grams does an empty jug weigh?
往一只空水壶里罐饮料，灌进两杯饮料连壶共重90克，灌进5杯饮料连壶共重138克．空水壶重多少克？
<gadget id="calculator">138 - 90</gadget>
<output>48</output>

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

<gadget id="calculator">48 / 3</gadget>
<output>16</output>

<gadget id="calculator">16 * 2</gadget>
<output>32</output>

<gadget id="calculator">90 - 32</gadget>
<output>58</output>

<result>58</result>