To simplify

First of all, Octavia error can be spotted from the correct steps below
Step1: Expand the expression

Step2: Collect like terms

Step 3: Simplify by using exponents laws

Step 4: Combine the terms.
The value is

Her error was that she didn't apply the exponents' law properly.
One of the laws she violated was

Her mistake was that she did

So she missed it from our step 1 above