Dad buys books online. This kind of book costs 100 yuan. Store A offers a 30% discount, and store B gets 19 yuan off for purchases over 69 yuan.
爸爸在网上买书，这种书100元，甲店打7折，乙店满69减19元，选哪个书店便宜，能省多少元？
<gadget id="calculator">19 * 1</gadget>
<output>19</output>

<gadget id="calculator">100 - 19</gadget>
<output>81</output>

<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">100 * (7/10)</gadget>
<output>70</output>

<gadget id="calculator">81 - 70</gadget>
<output>11</output>

<result>11</result>