Question 147891
Yes, you are doing it correctly.
Let's look at the equations to see why. 
1.{{{9x-5y=20}}}
2.{{{5y-9x=-20}}}
Re-arrange eq.2, x first then y,
2.{{{-9x+5y=-20}}}
Now, multiply both sides of eq. 2 by (-1),
2.{{{9x-5y=20}}}
You end up with eq. 1.
So yes, eq. 1 and eq. 2 are the same equation, as you already found out.
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With regards to fractions, remember they're just numbers. 
Maybe it's easier to change them to their approximate decimal values especially when graphing. 
Instead of (2 2/9,0) maybe try (2.2,0). 
It's usually close enough for graphing.