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Question

Solve by the elimination method~

7r - 6s = 21

6r + 7s = 103

What is the solution of the system?

Answer 1

(7r - 6s = 21)*6-------1

(6r + 7s = 103)*7---------------2

42r-36s=126-------------3

-42r+49s=721----------------4

    -13s=-595

    solve s

    and substitute the value in eq 1 2 3 or 4

    

thank u good friend

Answer 2

multiply the first equation by 7 (multiply each term in the equation) and the second by 6

    49r-42s=147

    35r+42s=618

add the two

    84r+0s=765

    r=9.107

substitute r value in first or second equation to find s

    7*9.107-6s=21

    s=7.124

    

Answer 3

Since you specified the solution to be via the elimination method,here are your steps:

Step 1 -- multiply the first equation 7r - 6s = 21 by 7, and you will have

49r - 42s = 147

Step 2 -- multiply the second equation by 6r + 7s = 103 by 6, and you will have

36r + 42s = 618

Step 3 -- add the two equations, i.e.,

49r - 42s = 147

36r + 42s = 618

______________

85r + 0 = 765

and solving for "r",

r = 9

Step 4 -- since "r" is now known, solve for "s" using any of the given original equations.

7(9) - 6s = 21

6s = 63 - 21

6s = 42

s = 7

ANSWER:

r = 9 and s = 7

Answer 4

The posts below mine made mistakes somewhere so here it is again because all the numbers came out clean.

7r-6s=21) <-- eq 1

(6r+7s=103) <-- eq 2

eq 1*7

eq 2 * 6

49r-42s= 147 <-- eq 3

36r+42s = 618 <-- eq 4

add eq 3 and eq 4 that will cancel out the s term

85r = 765

solve for r

r = 9

plug that back in eq 1 or eq 2 and you get s

7*9-6s=21

63-6s = 21

6s = 42

s = 7

Answer 5

7r - 6s = 21

7r = 21 + 6s

r = (21 + 6s)/7

Now we eliminate r

6r + 7s = 103

6*(21 + 6s)/7 + 7s = 103

Solve this for s.

Or (maybe is this elimination)

   7*(7r - 6s = 21)

   6*(6r + 7s = 103)

sum these two (s disappears -> 7*-6s + 6*7s = 0)

   7*(7r - 6s = 21)

   6*(6r + 7s = 103)

+---------------------------

7*7r+6*6r = 7*21+6*103.

Solve this for r