Final answer:
The expression that shows the number of buttons Nancy has left after giving away b buttons is 92 - b. This subtraction indicates the removal of b buttons from her original amount of 92 buttons.the correct answer is option a)
Step-by-step explanation:
The question involves an algebraic expression that represents a situation where Nancy has a certain number of buttons and gives some away. To determine how many buttons Nancy has left after giving away b buttons, we use subtraction. The correct expression to show the number of buttons she has left would be the total amount of buttons she originally had minus the number of buttons she gave away. Therefore, the expression is 92 - b.