Let #x# be the number of hectares purchased for #$2250#. Since we know the total number of hectares purchased was #100#, this leaves #(100-x)# hectares remaining.

What you're trying to find is #x#. We know the total cost of the land was #$215,000#, so if you take the number of hectares purchased for #$2250# #(x)# and multiply it by the price #(2250)#, then add that to the remaining hectares that you know were purchased for #$1850#, you get the following equation:

#2250x + 1850*(100-x) = 215000#

#2250x + 185000 - 1850x = 215000 " "larr# Distribute the #1850#

#400x = 30000 " "larr# Combine like terms

#x = 75 " "larr# Divide by #400#

This means that the number of hectares purchased at #$2250# was #75# and the remaining number of hectares #(100-75 or 25)# was purchased at #1850#.