The students of Sunshine Primary School participated in the tree planting activity, and assigned the tree planting task to the fourth, fifth and sixth graders according to the ratio of 3:4:5. As a result, the sixth graders planted 56 more trees than the fourth graders. How many trees were planted in the fourth, fifth and sixth grades?
阳光小学的同学参加植树活动，把植树任务按3：4：5分配给四、五、六年级学生，结果六年级同学比四年级多植树56棵，四、五、六年级共植树多少棵？
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<gadget id="calculator">3 + 4 + 5</gadget>
<output>12</output>

<gadget id="calculator">28 * 12</gadget>
<output>336</output>

<result>336</result>