Answer
The angle relative to the positive direction of the x axis is $~~-147^{\circ}$
Work Step by Step
In part (a), we found that $~~F_2 = -(32.0~N)\hat{i}-(20.8~N)\hat{j}$
We can find the angle of the force below the negative x axis:
$tan~\theta = \frac{20.8}{32.0}$
$\theta = tan^{-1}~(\frac{20.8}{32.0})$
$\theta = 33^{\circ}$
Therefore, the angle relative to the positive direction of the x axis is $~~-147^{\circ}$
