Let A be a 5 x 3 matrix. If $b = a_1 + a_2 = a_2 + a_3$
then what can you conclude about the number of solutions of the linear system Ax = b? Explain.
I'm not sure about this question. All I know is that if b can be written as a combination of column vectors a, then the linear system is consistent. I am not sure what this says about the number of solutions, however.