Teacher Zhang goes to the store to buy chalk for the school. White chalk is 0.8 yuan per pack, and colored chalk is 1.2 yuan per pack. If you want to buy white chalk with the money you bought for 20 packs of colored chalk, how many packs of white chalk can you buy?
张老师去商店给学校买粉笔，白色粉笔每包0.8元，彩色粉笔每包1.2元．要用买20包彩色粉笔的钱去买白色粉笔，能买白色粉笔多少包？
<gadget id="calculator">20 / 0.8</gadget>
<output>25</output>

<gadget id="calculator">1.2 * 25</gadget>
<output>30</output>

<result>30</result>