solve the given system of equations by the equations by the substitution method; 7x + 7y= 35 and -2x-y =8

Question

Solve x and y 

Answer 1

(1) 7x + 7y = 35

     Since each term has a 7, this can be divided out.

     x + 7 = 5

     Let y = 5 - x

 

(2)- 2x - y = 8

 

Substitue the first equation into the second equation:

 

-2x - (5 - x) = 8

-2x -5 + x = 8

-x = 13

x = -13

 

From (1), y = 5 - x = 18

 

The solution is x = -13 and y = 18

Answer 2

7x + 7y = 35                       -2x - y = 8       solve this equation for y

 

                                              + y = + y

 

                                             - 2x = y + 8

 

                                              - 8        - 8

 

                                         -2x - 8 = y      substitute this for y in first equation

 

7x + 7(-2x + - 8) = 35

 

      7x - 14x - 56 = 35

 

             - 7x - 56 = 35

                  + 56 = +56

 

                     -7x = 91

 

                        x = -13,   y = 18