A pen in a stationery store is 6.7 yuan, and a schoolbag is 34.5 yuan. I bought 3 pens and 4 schoolbags. How much should I prepare?
文具店一只钢笔6.7元，一个书包34.5元，淘气买了3支钢笔，4个书包要准备多少钱？
<gadget id="calculator">6.7 * 3</gadget>
<output>20.1</output>

<gadget id="calculator">34.5 * 4</gadget>
<output>138</output>

<gadget id="calculator">20.1 + 138</gadget>
<output>158.1</output>

<result>158.1</result>