Mods plz remove this one, i have posted in the right section now, i didn't want a advanced linear algebra answer.

This is a linear algebra question and i dont know how to solve for this because of the a,b, and c. i tried to do something but i dont know if its right.

I get the answer for part b as

x1 = a - c/3

x2 = -2b + b + c/3

x3 = 2a - b

Plz help me out and try to explain a bit if you can. I need help on a and b both.