First she bought 7 pairs of socks for $3 each
7 x 3 = $21
Then she bought she a sweater for her dog for $12
The total amount of money she spent:
$21 + $12 = $33
Then she found a $5 bill
So the difference of money is +5
She has 5 more dollars then what she had to begin with
Because she found $5, opposed to spending $33 of her money, she really spent $28 because she found $5
Hope this helps
-AaronWiseIsBae