Dad spent 400 yuan to buy a table, which is 80 yuan more expensive than buying a chair. How much did it cost to buy a set of such tables and chairs?
爸爸买一张桌子用了400元，比买一把椅子贵80元，买一套这样的桌椅一共用了多少元？
<gadget id="calculator">400 - 80</gadget>
<output>320</output>

<gadget id="calculator">320 + 400</gadget>
<output>720</output>

<result>720</result>