Xiao Zhang said: I have 13 balloons, 9 of which are red. Xiaoli said: It takes 7 to decorate the room. How many balloons are left.
小张说：我有13个气球，9个是红色的．小丽说：布置房间要用7个．还剩多少个气球．
<gadget id="calculator">13 - 7</gadget>
<output>6</output>

<result>6</result>