Each person was given 6 pieces of red paper and 15 pieces of yellow paper. After distributing to 18 students, there are 122 left. How many sheets of the two kinds of paper did you buy in total?
每人发6张红纸、15张黄纸．发给18个同学后，还剩122张．两种纸一共买了多少张？
<gadget id="calculator">6 + 15</gadget>
<output>21</output>

<gadget id="calculator">21 * 18</gadget>
<output>378</output>

<gadget id="calculator">378 + 122</gadget>
<output>500</output>

<result>500</result>