2nd pair of coordinates is wrong.

I have problem answering the next question. I keep getting the wrong answer. It should be 3 for z. But I get 3.8

You can look at my solution but I'm not sure if you've been taught to do it using matrix. If not I can show you using another method

We didn't use matrix method. We use substitution and elimination

I'm afraid that my lecturer can't accept matrix method since she's a little picky