(2 points) Consider the following Gauss-Jordan reduction:?

Decide what operation was being performed in each case. To find the matrix that implements that operation, simply perform the same operation on the identity matrix. So, since step 1 swapped rows 2 and 3, your answer is correct. That E_1 matrix is I with rows 2 and three swapped.
Your E_2 is off though. The operation seems to be adding three times row 3 to row 1. If you do that to the identity matrix you get:
[1 0 3]
[0 1 0]
[0 0 1]
That’s the E_2 matrix. Your answer applied the row operation to E_1 instead of I, so your answer is actually the matrix product E_2 E_1. That’s the matrix that performs both of the first two row operations.
Multiplying row 2 by -1/2 in step 3 is an E_3 matrix of:
[ 1 . 0 . 0 ]
[ 0 -1/2 0 ]
[ 0 . 0 . 1 ]
Try that thinking to get E_4 on your own.