Last year Eduardo invested at 8% interest and his wife Sofia invested some money at 9% interest. Their total on two investment was $860. This year each dicided to invest the same amount of money as last year Eduardo invested at 7% and Sofia invested hers at 6%. If they receive a total of $640 interest how much money did each invest

Eduardo invested $4000

Sofia invested $6000

Step-by-step explanation:

Let amount Eduardo invested be x

and amount Sofia invested be y. Then,

0.08x + 0.09y = 860 ⇒ 8x + 9y = 86000 ... (1) 0.07x + 0.06y = 640 ⇒ 7x + 6y = 64000 ... (2)

On solving equations (1) and (2),

We get, x = $4000 and substituting this value of x in (2), we get y = $6000

Hence, amount of money invested by each of them : Eduardo invested $4000 and Sofia invested $6000