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Select all the systems of equations that have exactly one solution.
y = 3x + 1, y = -3x + 7
y = 3x + 1, y = x + 1
y = 3x + 1, y = 3x + 7
x + y = 10, 2x + 2y = 20
x+ y = 10, x + y = 12 ​