Xiaofang has 20 sets of animal pictures, 4 in each set, 16 for her classmates, how many are left.
小芳有20套动物画片，每套4张，送给同学16张，还剩多少张．
<gadget id="calculator">4 * 20</gadget>
<output>80</output>

<gadget id="calculator">80 - 16</gadget>
<output>64</output>

<result>64</result>