First we draw a set of axis. Then we place the forces on them as shown in the first pciture.
As they are asking for the resultant force in the direction PQ we must resolve for forces in the y axis.
i.e. : 10 cos 30 + 10 cos 30 - 6 cos 60= 14.3 N
The direction 'perpendicular to PQ' is basically the x axis. So we resolve forces in the x axis.
10 cos 60 + 6 cos 30 - 10 cos 60 = 5.20 N
For the last part we know the magnitude of the horizontal and vertical forces. The resultant is the red line. (see 2nd pic)
Using Pythagoras Theorem : 5.2
2 + 14.3
2 = 231.53
Hence,
= 15.2 N (3 s.f.)