SOLUTION: Please help and thank you, also pls show solution to the problem, 3a-3b=-15 -3a-3b=-3 a=? b=?

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Question 727799: Please help and thank you, also pls show solution to the problem,
3a-3b=-15
-3a-3b=-3
a=?
b=?
Answer by hoomanc(14) About Me  (Show Source):
You can put this solution on YOUR website!
ok. just a simple explanation, assume,
D= -15 & N=-3 , you agree that D+N=-15-3=-18
it's exactly like that, sum the two equation with each other:
D >>> 3a-3b=-15
N >>> -3a-3b=-3
D+N >>> (3a-3a)+(-3b-3b)=-18
D+N >>> (-6b)=-18 >>>
b=3 >>>
(D >>> 3a-3*3=-15 >>> 3a =-15+9 =-6 )
a=-2