Ok, so I need to find a basis for subspace A.

A = {(x1, x2, x3) E R^3 | 2x1 + x3 = 0, x1 + x2 - x3 = 0} of R^3

I understand how to determine whether something is a basis of something else, but I cannot wrap my head around how to determine my own basis for this subspace.