posted by gail .
Solve the system of equations by graphing
y = 2, x = 3
for excellent graphs. Set the limits for x and y and let 'er fly.
The only inconvenience is that you need to express y as a function of x first.
For more versatile graphs, but less control over ranges, try
wolframalpha.com and enter
plot 2x+y=8, x+3y=9