need help, im confused

Answer:
Part A: correct
Part B: $20
Step-by-step explanation:
The amount Vanessa pays for her printer and 2 cartridges is ...
$90 +2(25) = $140
The amount Tia pays for her printer and 2 cartridges (c=2) is ...
t = 80 +20(2) = 120 . . . . dollars
Then the difference in the amounts they pay is ...
$140 -120 = $20