(21+24+27+…+63+66)-(11+14+17+…+53)=
(21+24+27+…+63+66)-(11+14+17+…+53)=
<gadget id="calculator">10 * 15</gadget>
<output>150</output>

<gadget id="calculator">150 + 66</gadget>
<output>216</output>

<result>216</result>