What is

3x-2y=9

y=2x-7

Since you know that "y" is equivalent to "2x - 7" you can substitute that into the first equation

3x - 2y = 9

3x - [2 (2x-7) ] = 9

3x - (4x - 14) = 9

3x - 4x + 14 = 9

-x + 14 = 9

-x = - 5

x = 5

y = 2x - 7

y = 2 (5) - 7

y = 10 - 7

y = 3

Okay, these get easy with practice so don't post all of these online. First, substitute y in 3x-2y=9 for what it says y equals (2x-7). You now have: 3x-2 (2x-7) = 9. Breakdown:

3x-2 (2x-7) = 9

3x-4x+14=9

-1x=-5

x=5

next solve for y

y=2x-7

y=2 (5) - 7

y=10-7

y=3

And now we have x=5, and y=3.