Solution - Linear equations with two unknowns

System of Linear Equations entered :

  [1]           y=3x-4-3
  [2]           y=-9x+12

Equations Simplified or Rearranged :

   [1]    y - 3x = -7
   [2]    y + 9x = 12

Graphic Representation of the Equations :

    -3x + y = -7        9x + y = 12  

  
 

Solve by Substitution :

// Solve equation [2] for the variable  y 
 

  [2]    y = -9x + 12

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

   [1]    (-9x+12) - 3x = -7
   [1]     - 12x = -19

// Solve equation [1] for the variable  x 

   [1]    12x = 19 

   [1]    x = 19/12 

// By now we know this much :

    y = -9x+12
    x = 19/12

// Use the  x  value to solve for  y 

    y = -9(19/12)+12 = -9/4 

Solution :

 {y,x} = {-9/4,19/12}