First 5.4 to the north that 2.1 to the south and finally 9.3 to the north solve for the magnitude of the resultant

Since you are asking for magnitude only, 12.6 units is the resultant. If you were looking for the full answer, 12.6 units North would be your answer

Explanation:

There there are 2 forces acting in the north direction add them up 5.4+9.3

this equals 14.7 since there is also something acting in the opposite direction, subtract that from the  total of the previous two, 14.7-2.1,

and your final answer will be 12.6 units

-4 on