(with lets say positive upwards). Then as the body is in equilibrium the
sum of each components is zero. so
Put phi = theta-10 degrees
p_1 = P(parrallel to Q) = -10 cos(10)
p_2 = P(orthog to Q) = -10 sin(10)
r_1 = R(parrallel to Q) = -R cos(phi)
r_2 = R(orthog to Q) = R sin(phi)
p_1 + r_1 = Q = -20
p_2 + r_2 = 0.
Which is a pair of simultaneous non-linear equationswhich you will have to
solve for phi and R.