Question 163240
I will show you how to apply it: 
for:
ax+by=e
cx+dy=f

We will have Cramer's rule giving us:

{{{x=(ed-bf)/(ad-bc)}}}
and
{{{y=(af-ec)/(ad-bc)}}}

So, just plug in the numbers for the problem we're interested in. Namely, a=1, b=2, c=1, d=-1, e=5, f=3.

The process is done automatically by this web site:


Check:*[invoke linear "x", "y", 1, 2, 5, 1, -1, 3 ]