Let "x" be the the area bought at $1850, measured in "ha". Then the remaining area is (100-x) ha. The "money equation" is 1850*x + 2250*(100-x) = 217000. Simplify and solve for x. 1850x + 225000 - 2250x = 217000, -400x = 217000 - 225000 = -8000 ====> x == = 20. Answer. 20 ha was bought at $1850. 100-20 = 80 ha was bought at $2250. Check. 20*1850 + 80*2250 = 217000. ! Correct !