21*42+21*63-21*5=how much.
21*42+21*63-21*5=多少．
<gadget id="calculator">21 * 42</gadget>
<output>882</output>

<gadget id="calculator">21 * 63</gadget>
<output>1_323</output>

<gadget id="calculator">21 * 5</gadget>
<output>105</output>

<gadget id="calculator">1_323 - 105</gadget>
<output>1_218</output>

<gadget id="calculator">882 + 1_218</gadget>
<output>2_100</output>

<result>2_100</result>