If the question is asking how many trees can be planted with 6 cubic yards of compost, here is the solution.
6 divided by 1/6 means to take 6 wholes and break them into groups the size of 1/6.
One whole can be broken into 6 groups of 1/6 (6/6), so 6 wholes can be broken into 36 groups of 1/6 (6 x 6 = 36/6).
Mathematically, you will multiply 6 by 6/1 to get the 36.
You can plant 36 trees with 6 cubic yards of compost.