Substitute this equation x+3y=18 & -x-4y=-25

 {x,y} = {3/7,-43/7}

Step-by-step explanation:

System of Linear Equations entered :

  [1]    x + 3y = -18

  [2]    -x + 4y = -25

Graphic Representation of the Equations :

   3y + x = -18        4y - x = -25  

Solve by Substitution :

// Solve equation [1] for the variable  x  

 [1]    x = -3y - 18

// Plug this in for variable  x  in equation [2]

  [2]    -(-3y-18) + 4y = -25

  [2]    7y = -43

// Solve equation [2] for the variable  y  

  [2]    7y = - 43  

  [2]    y = - 43/7  

// By now we know this much :

   x = -3y-18

   y = -43/7

// Use the  y  value to solve for  x  

   x = -3(-43/7)-18 = 3/7  

Solution :

{x,y} = {3/7,-43/7}

answer: y=0 if that is what u r looking for