Teacher Li bought a learning machine for 390 yuan and a power bank for 270 yuan. How much did Mr. Li spend in total?
李老师买了一个学习机390元，一个充电宝270元．李老师一共花了多少钱？
<gadget id="calculator">390 + 270</gadget>
<output>660</output>

<result>660</result>