Answer:
The amount invested in high-yield bonds was $20,000
Explanation:
The total amount Dorothy invested = $80,000
The amount that can be earned by investing part of the amount in high-yield bonds = 10% profit
The amount that can be earned by putting the rest of the amount into "old economy" stocks = 12% profit
Dorothy's total profit = $9,200
Let 'x' represent the amount she invested in high-yield bonds, and let 'y' represent the amount she invested in "old economy" stocks, we have;
x + y = 80,000...(1)
0.1·x + 0.12·y = 9,200...(2)
From equation (1), we get;
y = 80,000 - x
Plugging in the above value of 'y' in equation (2), gives;
0.1·x + 0.12·y = 0.1·x + 0.12 × (80,000 - x) = 9,200
0.1·x - 0.12·x + 9,600 = 9,200
-0.02·x = 9,200 - 9,600 = -400
x = -400/(-0.02) = 20,000
x = 20,000
The amount Dorothy invested in high-yield bonds, x = $20,000
(∴ y = 80,000 - x = 80,000 - 20,000 = 60,000
y = 60,000
The amount she invested in old economy stocks, y = $60,000).