During the winter vacation, the third grade students made 45 lanterns, and the number made by the third grade was 15 times less than that of the fourth grade. How many lanterns were made by the fourth grade?
寒假三年级同学制灯笼45个，三年级制作的个数比四年级的2倍少15个，四年级制作灯笼多少个？
<gadget id="calculator">45 + 15</gadget>
<output>60</output>

<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<result>30</result>