linear algebra least squares solution

Least-Squares Geometry.

Given the linear system of equations,

x

1 + x2 = 2

x

1 + x2 = 4

4.2.1. Least-Squares. Determine the least-squares solution to the linear system.

4.2.2. Least-Squares Error. Determine the least-squares error associated with the linear system.

4.2.3. Graphical Interpretation. Graph the linear system, the least-squares solution, and the least-squares error in R2.

For 4.2.1 I got x hat = [3 0]^T + x2[-1 1]^T this is the least squares solution right?

4.2.2 If the above is correct, I understand that the error would be found by ||b-Ax(hat)|| but If the above is correct I'm not sure what to do since x hat has two vectors. Can someone please show me?