Each pen is 6 yuan, and each exercise book is 3 yuan. Dongdong bought 4 pens and 1 exercise book. How much did Dongdong spend on buying the pens?
每支钢笔6元钱，每本练习本3元，东东买了4支钢笔和1本练习本，东东买钢笔用了多少元．
<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<result>24</result>