Solution - Linear equations with two unknowns

System of Linear Equations entered :

   [1]    3x - y = 4
   [2]    -15x - 5y = -20

Graphic Representation of the Equations :

    y + 3x = 4        -5y - 15x = -20  

  
 

Solve by Substitution :

// Solve equation [1] for the variable  y 
 

  [1]    y = 3x - 4

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

   [2]    -15x - 5•(3x-4) = -20
   [2]    -30x = -40

// Solve equation [2] for the variable  x 

   [2]    30x = 40 

   [2]    x = 4/3 

// By now we know this much :

    x = 4/3
    y = 3x-4

// Use the  x  value to solve for  y 

    y = 3(4/3)-4 = 0 

Solution :

 {x,y} = {4/3,0}