Master Li carries 100 pieces of glass, and the shipping fee for each piece is 0.8 yuan. If one piece is damaged, not only no freight but also 0.2 yuan compensation. After the glass arrived, Master Li received a shipping fee of 78 yuan. How many pieces of glass were damaged during the transportation?
李师傅承运100块玻璃，每块运费0.8元．如果损坏一块，不但没有运费还要赔偿0.2元．玻璃运到后，李师傅获运费78元，承运中损坏几块玻璃？
<gadget id="calculator">100 * 0.8</gadget>
<output>80</output>

<gadget id="calculator">0.2 + 0.8</gadget>
<output>1</output>

<gadget id="calculator">78 / 1</gadget>
<output>78</output>

<gadget id="calculator">80 - 78</gadget>
<output>2</output>

<result>2</result>