Is (2,3) a solution for the system ? y=2x + 4,
y=2x + 1

No it doesn't work for both therefore can't be a solution

To figure out if an ordered pair is a solution for a system of equations, you want to plug the ordered pair in and see if your result is true for BOTH equations.

y=2x + 4
y=2x + 1

plug in (2, 3)

(3) = 2(2) + 4 ... 3 = 4 + 4 ... 3 ≠ 8 
(3) = 2(2) + 1 ... 3 = 4 + 1 ... 3 ≠ 5

because the points do not give you a result like 3 = 3, they are not a solution for the system.