SOLUTION: Solve each system by addition: 4x+3= -3y -x/7 + 4y/21= 1 / are fractions I know the answer is (-3,3) can you show me how to do that?

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Solve each system by addition: 4x+3= -3y -x/7 + 4y/21= 1 / are fractions I know the answer is (-3,3) can you show me how to do that?      Log On


   

Question 329182: Solve each system by addition:
4x+3= -3y
-x/7 + 4y/21= 1
/ are fractions
I know the answer is (-3,3)
can you show me how to do that?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
(1) 4x%2B3=+-3y
(2) -x%2F7+%2B+4y%2F21=+1
first, I will get (1) into the same form as (2)
(1) +4x+%2B+3y+=+-3
Then I multiply both sides of (2) by 21
(2) -3x+%2B+4y+=+21
Now I multiply both sides of (1) by 3
(1) +12x+%2B+9y+=+-9
Now I multiply both sides of (2) by 4
(2) -12x+%2B+16y+=+84
Now I add (1) and (2)
25y+=+75
y+=+3
Then I substitute this result back into (1)
(1) 4x%2B3=+-3y
4x%2B3=+-3%2A3
4x+=+-3+-+9
4x+=+-12
x+=+-3
The answer is (-3,3)