Calculation: 7.8*2.1+7.8*8.9-7.8.
计算：7.8*2.1+7.8*8.9-7.8．
<gadget id="calculator">7.8 * 2.1</gadget>
<output>16.38</output>

<gadget id="calculator">7.8 * 8.9</gadget>
<output>69.42</output>

<gadget id="calculator">69.42 - 7.8</gadget>
<output>61.62</output>

<gadget id="calculator">16.38 + 61.62</gadget>
<output>78</output>

<result>78</result>