The students participated in the tree planting activity. How many were 85 trees planted in the fourth grade, and how many trees were planted in the third grade? (Complete the conditions first, and then formulate the solution.)
同学们参加植树活动，四年级植树85棵，多少，三年级植树多少棵？(先把条件补充完整，再列式解答．)
<result>10</result>