Students in a certain school volunteered to plant trees. A total of 75 trees were planted in the first 4 days, and an average of 30 trees were planted every day in the next 5 days. How many trees did these students plant on average every day?
某校学生义务植树，前4天共植树75棵，后5天平均每天植树30棵，这些学生平均每天植树多少棵？
<gadget id="calculator">30 * 5</gadget>
<output>150</output>

<gadget id="calculator">75 + 150</gadget>
<output>225</output>

<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">225 / 9</gadget>
<output>25</output>

<result>25</result>