Eliminate r:
Notice that the coefficients of r are 2 and 3.
Their common multiple is 6. We can cause the
r-terms to cancel if we multiply the first
equation through by (-3), and the second one
through by (+2)
Then you see that the coefficients of r are equal
in magnitude but opposite in sign, so the will
cance when we add those equations term by term.
---------------
Now we add straight down and the r terms cancel out
and we add the other terms
---------------
Now in a lot of cases we switch over to substitution,
but since 
is not an integers, it is better
to start all over and eliminate the other letter
instead.
--
Eliminate s:
Notice that the coefficients of s are 3 and 2.
Their common multiple is 6. We can cause the
s-terms to cancel if we multiply the first
equation through by (-2), and the second one
through by (+3)
Then you see that the coefficients of r are equal
in magnitude but opposite in sign, so the will
cance when we add those equations term by term.
---------------
Now we add straight down and the s terms cancel out
and we add the other terms
---------------
Edwin
