Solution - Linear equations with two unknowns

System of Linear Equations entered :

   [1]    x - y = 9
   [2]    x + y = 15

Graphic Representation of the Equations :

    y + x = 9        y + x = 15  

  
 

Solve by Substitution :

// Solve equation [2] for the variable  y 
 

  [2]    y = -x + 15

// Plug this in for variable  y  in equation [1]

   [1]    x - (-x +15) = 9
   [1]    2x = 24

// Solve equation [1] for the variable  x 

   [1]    2x = 24 

   [1]    x = 12 

// By now we know this much :

    x = 12
    y = -x+15

// Use the  x  value to solve for  y 

    y = -(12)+15 = 3 

Solution :

 {x,y} = {12,3}