First, count the sum of price for 3 pencils
pencils = 3 × price per pencil
pencils = 3 × 0.99
pencils = 2.97
The price of three pencils is $2.97
Second, count the sum of price for 2 packs of paper
paper = 2 × price per pack
paper = 2 × 2.50
paper = 5.00
The price of two packs is $5.00
Third, sum the prices and tax
price = paper price + pencil price
price = 2.97 + 5.00
price = 7.97
tax = 4% × 7.97
tax = 0.04 × 7.97
tax = 0.3188
total = 7.97 + 0.3188
total = 8.288
Total pay is $8.288, she has enough money to pay it.
Fourth, calculate the change
change = 20 - 8.288
change = 11.712
The change would be $11.71