There are a total of 63 pieces of RMB with 2 yuan and 5 yuan, totaling 171 yuan, how many pieces of 2 yuan are there?
有2元一张和5元一张的人民币共63张，共171元，则2元的有多少张．
<gadget id="calculator">5 * 63</gadget>
<output>315</output>

<gadget id="calculator">315 - 171</gadget>
<output>144</output>

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

<gadget id="calculator">144 / 3</gadget>
<output>48</output>

<result>48</result>