How to solve the system 2 x + 4 y = 8 and x +...

The graphical method isn't often used to solve any set of linear equations because it takes a long time, but take a look at it.
${\displaystyle x+y=1}$ put any 2 distinct values of x to get 2 distinct values of y .
like the set of values could be
${\displaystyle x=1y=0}$
${\displaystyle x=0y=1}$
do the same for other equation . plot these values on graph .since these are linear equations the graph would show a straight line .
the point at which the lines intersect is common solution .