If the equation (15*□-60)/3=□ is established, then how much should be filled in □.
若使等式(15*□-60)/3=□成立，则□应该填多少．
<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">15 * (1/3)</gadget>
<output>5</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<result>5</result>