Question 37760
The easiest way to graph a linear function is to rewrite it in slope-intercept form, {{{y=mx+b}}}.
m represents the slope, {{{rise/run}}}
b represents the y-intercept, x=0

{{{x-y=5}}}
{{{-y=-x+5}}}
You always want the y positive, so multiply the whole function by -1
{{{y=x-5}}}

{{{x+y=3}}}
{{{y=-x+3}}}

Now, graph the two lines.

{{{graph(400,400,-5,5,-5,5,x-5,-x+3)}}}
The answer for your system is where the two lines intersect. 
Answer: (4,-1) or {{{x=4}}} and {{{y=-1}}}
Hope this helps!