Question 404787
taking x+y=19 to be eqtn I and
       x-y=-7 to be eqtn II
if x and y have coefficients, you will have to choose from the two unknown x and y, which one to eliminate first by using the coefficient in either eqtn I or eqtn II to multiple all through what's on eqtn II and same to eqtn I respectively.

But since there is no coefficient there on the two variables, the add x to eliminate y: By doing so, you have;

add "x and x = 2x" , "+y and -y = 0", "19 and -7 = 12"
      2x+0=12, 2x=12, x=6.

substitute "x" in any of the 2 above eqtn but lets use eqtn I to find y:
    x+y=19
    6+y=19
      y=19-6
      y=13
     
      (x,y) (6,13)