Question 90431


    Solve the system by substitution.
3x – y = –7
x + y = –9

    3x-y = -7.........(1)

     x+y = -9..........(2)

       From eq'n (2) we get x = -9-y 
      substituing for x in eq'n (1) we get 3(-9-y)+y = -7 
                                          -27-3y+y = -7

                                             -2y = -7+27
                                              y = 20/-2 =  -10

      substituting the value of y in eq'n (2),we get x-10 = -9
                                                     x = 10-9 = 1

      The values of x = 1 and y = -10 are the required solution for the given eq'n