Mom divided a watermelon into 10 pieces on average, father and mother each ate 3 pieces, and Miao Miao ate the rest. How much of this watermelon did Miao Miao eat?
妈妈把一个西瓜平均分成10块，爸爸和妈妈各吃了其中的3块，剩下的都给苗苗吃．苗苗吃了这个西瓜的多少．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 3</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10) - (3/10)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>