Given lines:
$2y = x + 1$ and $y = 3x + 2$.
From $2y = x + 1$
we get $y = \dfrac{1}{2}x + \dfrac{1}{2}$,
so slope $m_1 = \dfrac{1}{2}$.
From $y = 3x + 2$,
slope $m_2 = 3$.
Angle between two lines:
$ \tan\theta = \left|\dfrac{m_2 - m_1}{1 + m_1 m_2}\right| $
$ \tan\theta = \left|\dfrac{3 - \dfrac{1}{2}}{1 + \dfrac{1}{2}\cdot 3}\right|
= \dfrac{\dfrac{5}{2}}{\dfrac{5}{2}} = 1 $
So $\theta = 45^\circ$ or $135^\circ$.
Required obtuse angle $= 135^\circ$.