SOLUTION:
We want to construct the augmented matrix for these equations;

We start by writing the equations with variables on the right and constants on the left; multiplying equation 1 by 3, we have;

Expanding equation 2 and collecting like terms, we have;

Expanding equation 3 and collecting like terms, we have;

Writing the 3 equations, we have;

Putting this in augmented matrix form we have;

Which is the final answer