Final answer:
The expression that does NOT represent the cost of dinner plus a 26% tip is option c, which is d + 0.26d. This option is listed twice, signifying a mistake.
Step-by-step explanation:
The question asks which expression does NOT represent the cost of dinner plus a 26% tip if dinner costs d dollars. We know that a 26% tip on the dinner cost d is represented by 0.26d. Therefore, to calculate the total cost including tip, we would add the tip to the original cost, which is represented by d + 0.26d or as a single expression, we can write it as 1.26d (or d(1 + 0.26)).
Let's analyze each option:
- (1 + 0.26)d = 1.26d, which is the correct expression for the cost including tip.
- d + 0.26d = 1.26d, which also correctly represents the total cost.
- 1d + 0.26d simplifies to 1.26d, which is correct.
- d + 0.26d, as listed twice, is not a unique expression and hence, this duplication indicates a potential error or oversight. This is the option that does NOT accurately represent a unique approach or formula for adding the tip.
Therefore, the correct answer to the student's question would be option c (d + 0.26d), given its repetitive nature.