Answer
$v=140\frac{m}{s}$
Work Step by Step
We know that
$v=\sqrt{\frac{T}{\mu}}$
where 'T ' is the tension in guitar and $'\mu'$ represent linear mass density.
Putting the values, we get
$v=\frac{150N}{7.2\times10^{-3}\frac{Kg}{m}}$
$v=140\frac{m}{s}$
