Question 7 - A-Level Maths

1. Given that $\mathbf { M }$ is a non-singular matrix, find $\mathbf { M } ^ { - 1 }$ in terms of $k$
  7
(ii) State any restrictions on the value of $k$ 7
Using your answer to part (a)(i), solve $$\begin{array} { r } x + 7 y - 3 z = 6
3 x + 6 y + 6 z = 3
x + 3 y + 2 z = 1 \end{array}$$