Question

Margie's work for adding linear expressions is shown below. After checking her answer with the answer key, she solved it incorrectly.

Given (−2.67b + 11) − (3.71b − 15)
Step 1 −2.67b + 11 + −3.71b − 15
Step 2 −2.67b + −3.71b + 11 − 15
Step 3 (−2.67b + −3.71b) + (11 − 15)
Step 4 −6.38b + (−4)


Part A: Identify and explain the first step where Margie made an error. (6 points)

Part B: Explain how to correctly write the expression in fewest terms by correcting the error in Part A. Show all work. (6 points)

Answer 1

I need my bread gang so sorry 45

Answer 2

My solution

↓

Given (−2.67b + 11) − (3.71b − 15)

Step 1 • -2.67b + 11 - 3.71b + 15 Margie's error is that she did not multiply -15 by -1 to get +15. She instead got -15

Step 2 • -2.67b - 3.71b + 11 + 15 No error except the +15

Step 3 • (-2.67b - 3.71b) + (11 + 15) I don't understand what this step is for: Margie has already grouped the like terms in the last step. No error except the +15

Step 4 • -6.38b + 26 No error except the +26 that came from the +15 mistake

Step 5 • 26 - 6.38b Shuffling the terms around to make it a bit neater

Margie's error was in step 1. Her error is that she did not multiply -15 by -1 to get +15. She instead got -15