Since the expression:
represents the amount each friend pays, and x is the amount of the bill before the tip, and the tip is divided in 4 for each friend to pay the same amount, then the expression:
Is a quarter of the total amount of the bill, and represents the amount each friend pays toward the bill.
Since each friend pays $2 in addition, the term 2 represents the amount each friend pays toward the tip.
Since Talia will pay twice the amount that each friend is supposed to pay, then the expression which represents the total amount that Talia will pay, is: