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
