Answer:
$4000 is invested in the account which earning 3% rate .
Explanation:
Formula

As given
$6,000 dollars is invested in two different accounts earning 3% and 5% interest.
At the end of one year, the two accounts earned $220 in interest.
Let us assume that the x amount is invested in the account which earning 3% interest .
Let us assume that the (6000 - x ) amount is invested in the account which earning 3% interest .
Thus the equation becomes

Simplfy the above equation
22000 = 3x + 30000 - 5x
30000 - 22000 = 5x - 3x
8000 = 2x

x = $4000
Therefore $4000 is invested in the account which earning 3% rate .