Answer:
$39
Step-by-step explanation:
The cost of the treat was $30, with the addition of a 10% sale tax and a 20% tip on the original $30.
So, total of (10 + 20) = 30% extra cost she has to pay on the original $30.
Hence, the total amount to be paid for the meal will be
[tex]30(1 + \frac{30}{100}) = 39[/tex] dollars. (Answer)