To find the abscissa of point \( P \), we first determine the equation of the line connecting points \( (1, 2) \) and \( (5, 6) \).
The slope of this line is: \[ m = \frac{6 - 2}{5 - 1} = 1 \] The equation of the line is: \[ y - 2 = 1(x - 1) \quad \Rightarrow \quad y = x + 1 \] Now, since the point \( P \) is on the \( x \)-axis, its \( y \)-coordinate is 0.
Substituting \( y = 0 \) into the equation of the line: \[ 0 = x + 1 \quad \Rightarrow \quad x = -1 \] Thus, the abscissa of the point \( P \) is 2.