First, find the number of driveways Paula has shovelled to earn $144
$144 ÷ $12 = 12
She has shovelled 12 driveways to earn $144.
Second, find the number of driveways she shovelled on Sunday given that she has already shovelled 6 driveways on Saturday.
12 - 6 = 6
She shovelled another 6 driveways on Sunday.
Answer: 6 driveways