To analyze the transformation from the original ordered pair (8, 21) to the transformed ordered pair (2, 21), we can consider the changes in the x-coordinates.
The original x-coordinate is 8, and after the transformation, the new x-coordinate is 2.
To determine the value of k, we can use the formula for horizontal transformations, which states that if you have a transformation of the form \( (x, y) \) to \( (kx, y) \), then:
\[ k = \frac{\text{new x}}{\text{original x}} = \frac{2}{8} = \frac{1}{4}. \]
Since \( k = \frac{1}{4} \), this indicates a horizontal compression because the value of k is less than 1. A horizontal compression means that every x-coordinate is being squeezed closer to the y-axis.
Therefore, the correct choice is:
1/4; compression.