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.
