Answer
$B = 68.6^0$
$F_B =960N $
Work Step by Step
$Note:$ B is the angle made by Force $F_B$ wrt -ve x-axis
* Summing the force components in X, we have
$F_{x} = 0$
$700 Sin 30° - F_B Cos B =0$
$ F_B Cos B =700 Sin 30°$
$ F_B Cos B =350$
* Summing the force components in Y, we have
$F_{Y} = 1500$
$700Cos 30° + F_B sin B =1500$
$ F_B sin B =1500-700 Cos 30°$
$ F_B sin B =893.8$
$tanB =\frac{SinB}{CosB}$
$B = tan^{-1}[\frac{893.8}{350}]$
$B = 68.6^0$
* Put B in Either of the two Equations
$F_B =960N $
