Question 182242
 2c-d=-2 
 4c+d=20
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This is called a system of equations.
You are asked to find a solution that
satisfies both equations.
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Add the two equation to solve for "c":
6c = 18
c = 3
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Substitute into 2c - d = -2 to solve for "d":

2*3 - d = -2
d = 8
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Check the answer in both equations:
2c-d=-2
2*3 - 8 = -2
6 - 8 = -2
-2 = -2
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 4c+d=20
4*3 + 8 = 20
12 + 8 = 20
20 = 20
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Both check out so the solution is c=3, d=8
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Cheers,
Stan H.