SOLUTION: a+b=20 5a+9b=120 solve for b

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Question 1018559: a+b=20
5a+9b=120
solve for b
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
Can do this by substitution or elimination. Let me substitute. a+b=20, a=20-b
5(20-b)+9b=120
100-5b+9b=120
4b=20
b=5
a=15
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check in second equation
5(15)+9(5)=120, and that checks.