A good answer might be:

Can it be done? Yes, but you might be worried, at first. 

a( -1, 5 )T + 2( 3x, 10 )T = ( 8, 25 )T
 ( -a, 5a)T +  ( 6x, 20 )T = ( 8, 25 )T
         ( 6x-a, 5a+20 )T  = ( 8, 25 )T

Equating corresponding elements: 

6x-a  =  8
5a+20 = 25;  5a = 5;  a = 1

6x-1  =  8;  6x = 9;  x = 9/6 = 3/2

Scaling with values less than One

In the definition of scaling: 

a( x, y )T = ( ax, ay )T

it is OK if "a" is smaller than one. For example: 

0.5( x, y )T  =  ( 0.5*x, 0.5*y )T

Sometimes this is written as: 

( x, y ) 
--------   =   ( x/2, y/2 )  
   2

QUESTION 8:

(Review: ) What is the length of (1,0)T ?