The simplest vector you can take along the x-axis is \(\mathbf v=langle1,0,0\rangle\).
Now,
\(\mathbf b\cdot\mathbf v=\|\mathbf b\|\|\mathbf v\|\cos\theta\)
where \(\theta\) is the angle between the two vectors. You have
\(\mathbf b\cdot\mathbf v=\langle4.4,9.6,5\rangle\cdot\langle1,0,0\rangle=4.4\)
\(\|\mathbf b\|=\sqrt{4.4^2+9.6^2+5^2}\approx11.68\)
\(\|\mathbf v\|=\sqrt{1^2+0^2+0^2}=1\)
so that
\(4.4=11.68\cos\theta\implies\cos\theta=0.3767\implies \theta\approx67.87^\circ\)
