Answer:
non linear ( ꈍᴗꈍ)( ╹▽╹ )( ╹▽╹ )
X + y = 120000
0.15x - 0.10y = 5500
Multiply both sides of bottom by 100 to remove decimals
x + y = 120000
15x - 10y = 550000
Multiply both sides of top by 10
10x + 10y = 1200000
15x - 10y = 550000
Add the two
25x = 1750000
x = 70000
He paid $70,000 for the property that made a profit, and paid $50,000 for the property that lost value.
The length is 30 meters and the width is 12 meters.
You can go through the effort of determining the zero of the function analytically and evaluating an analytic expression for the derivative at that point, or you can let a graphing calculator do that heavy lifting. Since the numbers have to be "nice" for your equation to have the desired form, it is easy to know what to round to in the event that is necessary (it isn't).
We find the positive zero-crossing at x=2, and the slope of the curve at that point to be 8. Thus the line will have slope -1/8 and can be written as
.. x +8y -2 = 0