SOLUTION: Solve this system of equations using the elimination method: 3a-3b=-15 -3a-3b=-3 please explain steps thank you

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Question 612885: Solve this system of equations using the elimination method:
3a-3b=-15
-3a-3b=-3
please explain steps
thank you
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Simply add the equations to get

3a-3b=-15
-3a-3b=-3
---------
0a-6b=-18

So

-6b = -18

b = -18/(-6)

b = 3

Now that we know that b = 3, we can use this to find 'a'.

3a-3b=-15

3a-3(3)=-15

3a-9=-15

3a=-15+9

3a=-6

a = -6/3

a = -2

So the solutions are a = -2 and b = 3 giving us the ordered pair (-2,3)