A block kept on a rough inclined plane, as shown in the figure,...

$2 + mgsin \theta = \mu mgcos \theta$

$mgsin \theta - \mu mgcos \theta = 2 . . . . . . . . \left(1\right)<br />$mgsin \theta + \mu mgcos \theta = 10 . . . . . . . \left(2\right)$</p><p>equation (1) devided by (2)<br /><br />$\dfrac{mg\left(sin \theta - \mu cos \theta\right)}{mg\left(sin \theta + \mu cos \theta\right)} = \dfrac{- 2}{10} = \dfrac{- 1}{5}$<br /><br />\left(1 - \mu\sqrt{3}\right)5 = - \left(1 + \mu\sqrt{3}\right)$

$6 = 4\sqrt{3}\mu$

$\mu = \dfrac{\sqrt{3}}{2}$