(15,-9) is dilated by a scale factor of 3 what is its new location

For this case what you should do is follow the following transformation:
 (x, y) ---> k (x, y) ---> (kx, ky)
 Applying the transformation to the ordered pair we have:
 (15, -9) ---> 3 (15, -9) ---> ((3) * (15), (3) * (- 9)) > (45, -27)
 
 its new location is: 
 (45, -27)