Using the parallelogram of forces, F, the other force=√(50^2+70^2-7000cos(100-35))=66.6459N approx.
Using the sine rule, sin65/F=sin(x+80)/70 where x is the angle of F and 80 is the supplementary angle of the 50N force. sin(x+80)=70sin65/F=0.9519. Therefore x+80=72.16, x=-7.84 or 352.16°.