The magnitude of vector $ \vec{v} $ is $ \| \vec{v} \| = \dfrac{ 59 }{ 5 } $ .
To find magnitude of a vector $ v=(a,b) $ we use formula $ ||v|| = \sqrt{a^2+b^2} $
In this example $ a = \frac{ 59 }{ 5 } $ and $ b = 0 $, so:
$$ ||v|| = \sqrt{ \left(\frac{ 59 }{ 5 }\right)^2 + 0^2 } = \sqrt{ \frac{ 3481 }{ 25 } + 0 } = \sqrt{ \frac{ 3481 }{ 25 } } = \frac{ 59 }{ 5 }$$