A block of mass 200g is kept stationary on a smooth inclined plane...

Balancing the forces in horizontal direction $Nsin\theta = F$

And balancing the forces in vertical direction $Ncos\theta = mg$

$⇒ tan\theta = \dfrac{F}{mg}$$⇒ F = mgtan\theta$

$F = 0 . 2 \times 10 \times \sqrt{3} = \sqrt{12}N$. Therefore, $x = 12$