Mom bought 4.5 kilograms of tomatoes, gave the salesperson 20 yuan, got back 6.5 yuan, how much is it per kilogram of tomatoes?
妈妈买了4.5千克西红柿，给售货员20元，找回6.5元，每千克西红柿多少元？
<gadget id="calculator">20 - 6.5</gadget>
<output>13.5</output>

<gadget id="calculator">13.5 / 4.5</gadget>
<output>3</output>

<result>3</result>