As it is given that 2 kg mass is suspended by 12 cm long thread and then a horizontal force is applied on it so that it remains in equilibrium at 30 degree angle
So here we can use force balance in X and Y directions
now for X direction or horizontal direction we can use

for vertical direction similarly we can say

so here we first divide the two equations



now plug in all values in the above equation


Part b)
now in order to find the tension in the thread we can use any above equation




so tension in the thread will be 22.6 N