Each cake is 5 yuan, and Zhang Ming buys 6 cakes with 100 yuan, how much should he get back?
每块蛋糕5元，张明用100元去买6块蛋糕，应找回多少元？
<gadget id="calculator">5 * 6</gadget>
<output>30</output>

<gadget id="calculator">100 - 30</gadget>
<output>70</output>

<result>70</result>