SOLUTION: Solve the following systems by substitution. Substitute the expression in the second equation into the first equation and solve. x-y=4

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Question 242780: Solve the following systems by substitution. Substitute the expression in the second equation into the first equation and solve.
x-y=4 y=2x+6
Answer by oberobic(2304) (Show Source):
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The question gives the method for solving the question. The first equation is x-y=4. The second equation defines y=2x+6. Substituting the right-hand side of the second equation in place of y in the first equation obtains: x - (2x+6) = 4. This becomes x - 2x - 6 = 4, or -x - 6 = 4. Add 6 to both sides, we have: -x = 10. Multiply by -1 to obtain: x = -10.
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Substituting in the second equation: y = 2(-10) + 6 = -20 + 6 = -14.
Substituting in the first equation: x - y = 4, which is -10 - (-14) = -10 + 14 = 4.