Answer:
$82.57
Step-by-step explanation:
The tip they leave is ...
$78.64 × 0.20 = $15.73
The amount of the discount is ...
$78.64 × 0.15 = $11.80
Then the total cost of the meal and tip is ...
meal price - discount + tip
$78.64 -11.80 +15.73 = $82.57