11*2+12*3+13*4+...+18*9+19*10.
11*2+12*3+13*4+…+18*9+19*10．
<gadget id="calculator">20 + 100</gadget>
<output>120</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">120 * (9/2)</gadget>
<output>540</output>

<gadget id="calculator">540 + 330</gadget>
<output>870</output>

<result>870</result>