Answer:
First I would add $3.99, $1.29, and $6.75 to see the total amount she spent.
3.99 + 1.29 + 6.75 = 12.03
She spent a total of $12.03. Now, subtract this amount from $20 to get your answer.
20 - 12.03 = 7.97
She should receive $7.97 in change.
I hope this helps!
-Mikayla