To find the length of the side formed by the vertices \((-2, 5)\) and \((9, 5)\), we can calculate the distance between these two points. Since both points have the same y-coordinate, the distance is simply the difference in their x-coordinates.
The formula for the distance between two points \((x_1, y_1)\) and \((x_2, y_2)\) is:
\[ d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]
In this case:
- \(x_1 = -2\)
- \(y_1 = 5\)
- \(x_2 = 9\)
- \(y_2 = 5\)
Calculating the distance:
\[ d = \sqrt{(9 - (-2))^2 + (5 - 5)^2} \] \[ = \sqrt{(9 + 2)^2 + 0^2} \] \[ = \sqrt{11^2} \] \[ = \sqrt{121} \] \[ = 11 \]
Thus, the length of the side formed by these vertices is
\[ \boxed{11} \text{ units} \]