In order to plant poplar trees in the school, teachers and students in the fifth and fourth grades set up volunteer teams respectively. Each volunteer team formed 15 groups. tree pits, how many tree pits were dug in total?
为了栽学校的杨树林，五年级和四年级的师生分别成立了志愿队，每个志愿队成立了15个小组，五年级每个小组挖了12个树坑，四年级每个小组挖了8个树坑，一共挖了多少个树坑？
<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<result>300</result>