Point satisfying a system of equations

Does the point (1, 20) satisfy the following system of equations?
y = -2x + 15
y = x + 12

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Substitute 1, in for x, and 20, in for y, into both equations.
If you get a true statement, then yes, the point satisfies the system

y = -2x + 15
20 = -2(1) + 15   {substituted in}
20 = -2 + 15   {multiplied}
20 = 13   {added on right}

- this is a false statement, so no the point does not satisfy the system
- no need to check in other equation 

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