21. you can first start by seeing that since two pairs of socks are $6, then one pair must be $3. So, by multiplying 6 by 3, you would get 18 which would show that the socks would cost $18.
22. By dividing 15 by 3, you can deduce that an hour of cleaning would yield $5. So, by multiplying that by 15, she would earn $75.
