2x + y = 8
x + y = 4
The lines intersect at
x + y = 4
The lines intersect at

These are simultaneous equations, they can be solved by addition.
you need first to get rid of y or x to find the value of the other one:
I'll multiply the first equation by 1 to get red of y:
so, the two equations are
2xy = 8
x + y = 4
now, add the two equations you'll get
x = 4 > x = 4
now, substitute the value of x in any of the equations to get the value of y
4+y = 4 y =0
so, the lines intersect at (4,0)
you need first to get rid of y or x to find the value of the other one:
I'll multiply the first equation by 1 to get red of y:
so, the two equations are
2xy = 8
x + y = 4
now, add the two equations you'll get
x = 4 > x = 4
now, substitute the value of x in any of the equations to get the value of y
4+y = 4 y =0
so, the lines intersect at (4,0)

At the point they intersect, both are true for the same value of x and y , thus it is OK to combined the two equations.
2x + y = 8 .......i
x + y = 4..........ii
subtract ii from i
x + 0 = 4
x= 4
substitute in ii
4 + y = 4
y = 0
2x + y = 8 .......i
x + y = 4..........ii
subtract ii from i
x + 0 = 4
x= 4
substitute in ii
4 + y = 4
y = 0

(4,0)
mutiply the second equation by 1 u should get xy=4 then add it to the 1st equation and u should get x=4 so u substitute it into any equation the second is easier so it would be 4+y=4 then subtract 4 from both sides so y=0
mutiply the second equation by 1 u should get xy=4 then add it to the 1st equation and u should get x=4 so u substitute it into any equation the second is easier so it would be 4+y=4 then subtract 4 from both sides so y=0

First put it in its original form:
y = 2x + 8 and
y = x + 4
Then draw the line.
y = 2x + 8 and
y = x + 4
Then draw the line.