Dorothy invested $80,000. Some was invested in high-yield bonds that earned a 10% profit,
and the rest was put into “old economy" stocks
that earned a 12% profit. How much did
Dorothy invest in high-yield bonds if her total
profit on both types of investments was
$9,200?

The amount invested in high-yield bonds was $20,000

Step-by-step 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).

Step-by-step explanation:

slope=(y2-y1)/(x2-x1)

where (x1,y1)=(-8,-3)

(X2, y2)=(-12,-3)

slope=(-3+3)/(-12+8)=0