Answer: C. (1,4)
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The graphs cross at this point. Intersection points are solutions to systems of equations.
Put another way, (1,4) is on the blue line and on the red line simultaneously.
A point on the red line is a solution to the red equation. A point on the blue line is a solution to the blue equation.
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Checking the answer:
y = x+3
4 = 1+3 ... plug in x = 1 and y = 4 into the blue equation
4 = 4 .... solution works for the blue equation
y = 3x+1
4 = 3(1)+1 ... plug in x = 1 and y = 4 into the red equation
4 = 3+1
4 = 4 ... solution also works for the red equation
This fully confirms the solution