Line the equations up like this:

 

To make the y terms cancel, multiply the
bottom equation through by 2, which will 
make the 2y term become 4y which will 
cancel with the -4y term in the top equation,
when we add equals to equals



Adding term by term gives:



  

Since that is a nasty fraction, do not substitute it,
as you would if it had been a nice integer. Instead, 
start over and eliminate the other variable:

 

To make the x terms cancel, the LCM of 15 and 9 is
45.  So we multiply the top equation through by 3,
and the bottom equation through by -5, which will 
make the 15x term become 45x, and the 9x in the
bottom equation become -45x which will cancel when 
we add equals to equals:



Adding term by term gives:



            

             



Edwin