Encoding/Decoding Matrices

My Algebra 2 teacher is telling us to use matrices to encode messages, and put them into Microsoft Excel. Here are the steps on the paper

Use coding sequence a=1, b=2-z=26

1. encode "I AM GOOD AT MATH" using 1x3 matrices. Do this on a sheet of paper(7th deliverable)

2. Enter the 1x3 matrices into Excel, leaving an empty cell between each matrix

3. Encode each 1x3 "plain text" matrices using the matrix below (9th deliverable - a 3x3 matrix plus six seperate 1x3 matrices)

4. Matrix: row 1: 1 2 1, row 2: 2 1 2, row 3: -1 0 1 a 3x3 matrix plus six separate 1x3 matrices

5. Get the determinant of this matrix to ensure it is not zero

6. Invert the matrix (11th deliverable)

7. Use this matrix to decode the encrypted 1x3 matrices from step "4" (12 deliverable - 6 separate 1x3 matrices)

8. After printing your results, circle and label each deliverable