To determine if the ordered pair (2,4) is a solution of the equation y=x+4, you have to replace the equation with the x-coordinate of the given ordered pair and calculate the corresponding value of y. Then you have to compare both y-values
The coordinates of the ordered pair are:
x=2
y=4
Replace the equation with x=2 and calculate the value of y:

The calculated y-coordinate is y=6, but the given y-coordinate is y=4, this indicates that the ordered pair (2,4) is not a solution of the equation.