When Benben calculates 15+(1/2)*□, he calculates 15+(1/2) first by mistake, and the calculated result is less than the correct result. 3. What is the number in □?
笨笨在计算15+(1/2)*□时，错误地先算15+(1/2)，这样算出的结果比正确结果少3．□中的数是多少？
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) - (1/2)</gadget>
<output>0</output>

<gadget id="calculator">15 + 0</gadget>
<output>15</output>

<gadget id="calculator">12 / 15</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>