Question

find the value of Q in the system so that the solution to the system is

x-3y=4
2x+Qy=8

Answer 1

 x -3y = 4  multiplie both sides by -2 => -2x +6y = -8 
2x +Qy = 8

-2x +6y = -8
 2x +Qy = 8
------------------ assume the same terms 
  0 6y +Qy = 0

6y +Qy = 0 

Qy = -6y  divide both sides by y and will get 

Q = -6