Dolbe the following system of equations 2x+y=3, x=2y-1

First off, I changed the second equation so that it resembled the first one, it became,
x - 2y = -1
Then because I prefer elimination method I chose to multiply one of the equations so that a variable could be eliminated.
2x + y = 3 multiplied by 2 gave me,
4x + 2y = 6

Now you can set them up for elimination.
4x + 2y = 6
+(x - 2y = -1)
_________
5x = 5
Thus x = 1.
Now you can take this new value and put it into one of the original equations to solve for the other variable.
(1) - 2y = -1
-2y = -2
y = 1.
Hope this helps! :)