Answer:
a=-4, b=-4. (-4, -4).
Step-by-step explanation:
-3a+7b=-16
-9a+5b=16
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-3(-3a+7b)=-3(-16)
-9a+5b=16
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9a-21b=48
-9a+5b=16
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-16b=64
b=64/-16
b=-4
-3a+7(-4)=-16
-3a-28=-16
-3a=-16+28
-3a=12
a=12/-3
a=-4
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