Question

If the two lines 2x + y= 0 and y=3 are plotted on a typical xy coordinate grid, at which point will they intersect?

Answer 1

2x + y = 0
2x + 3 = 0
      - 3  - 3
      2x = -3
       2      2
         x = -1¹/₂
(x, y) = (-1¹/₂, 3)

Answer 2

We have
equation 1   $2x+y=0$

equation 2  $y=3$

substitute the equation 2 in equation 1
$2x+[3]=0 \\ 2x=-3 \\ x=- \frac{3}{2}$

the solution is the point
$(- \frac{3}{2} ,3)$

using a graph tool
see the attached figure