The given system of equation :
x +2y =4
2x -2y =5
On adding both equation we get
x+2y+2x-2y=4+5
3x=9
x=3
So, for y, substitute x=3
x+2y=4
3+2y=4
2y=4-3
2y=1
y=1/2
The solutions is (3,1/2)
The system of linear equation have infintely many solution if they are coincidient, i.e. slope are equal
The given expression :
x+2y =4
2y=4-x
y=(4-x)/2
y = 2-x/2
So slope is (-1/2)
The second equation : 2x-2y=5
2y=2x-5
y=(2x-5)/2
y=x-