SOLUTION: solve each system using the substitution method. x-2y=7 3x-21=6y

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Question 302020: solve each system using the substitution method.
x-2y=7
3x-21=6y
Answer by london maths tutor(243) About Me  (Show Source):
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x-2y=7 ... equation 1
3x-21=6y ... equation 2
Let's x = 1
x-2y = 7
1 - 2y = 7
-2y = 7 -1
-2y = 6
y = -3
Put y = -3 and x = 1 into equation 2
3x - 21 = 6y
3x - 6y = 21
3(1) - 6(-3) = 21
3 -(-18) = 21
3 + 18 = 21
21 = 21
Therefore, x = 1 and y = -3