Precalculus, Chapter 6, 6.3, Section 6.3, Problem 50

You need to find the component form of the vector v = , hence, you need to use the information provided.
You need to evaluate the magnitude |v|, such that:
|v| = sqrt(a^2+b^2)
3 = sqrt(a^2+b^2)
The direction angle of the vector coincides to the direction angle of the vector u = <-12,-5> ,such that:
tan theta = b/a => tan theta = 5/12 => b/a = 5/12 => b = a*5/12
Replacing a*5/12 for b yields:
3 = sqrt(a^2+a^2*25/144)=> 3 = +-13a/12=> a = +-36/13
b = +-(36/13)*(5/12)
b = +-15/13
Hence, evaluating the components of the vector v, yields <+36/13 ,15/13> or <-36/13 ,-15/13>.