Answer
$(a)\space 78N$
$(b)\space \theta=34^{\circ}$
Work Step by Step
Please see the attached image first. The triangle was drawn according to a scale
The head of $F_{3}$ touches the tail of $F_{1},$ because the resultant of the three forces is zero.
(a) If the resultant force acting on the ball is zero, from the figure we can measure $F_{3}$ must have a magnitude of 78 N
(b) By using the protractor we can measure the angle $\theta=34^{\circ}$
