A regular polygon of 6 sides is formed by bending a wire of length...

Direction of magnetic field due to all six sides will be in the same direction, therefore we can write 

$B = 6\left(\dfrac{{\mu}_{0}I}{4\pir}\right)\left(\sin 30 ° + \sin 30 °\right)$, where $r =$distance of the sides from the centre.

$= 6\dfrac{{10}^{- 7} \times 4\pi\sqrt{3}}{\left(\dfrac{\pi}{3} \times \sqrt{3}\right)}$

$= 72 \times {10}^{- 7}T$

Hence, $x = 72$.