Beibei divides a cake into 7 parts on average, 3 pieces for mother and 2 pieces for father, what fraction of the cake does he have left?
贝贝把一只蛋糕平均分成7份，给妈妈3块，给爸爸2块，自己还剩下这只蛋糕的几分之几？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (3/7) - (2/7)</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>