The two reactant forces on the ladder are:
- \( F_{\text{wall on ladder}} \) - The force exerted by the wall on the ladder.
- \( F_{\text{ground on ladder}} \) - The force exerted by the ground on the ladder.
Therefore, the correct notation for the forces would be \( F_{\text{wall on ladder}} \) and \( F_{\text{ground on ladder}} \).
In terms of Newton's Third Law, these forces can be described as equal in magnitude and opposite in direction to the forces the ladder exerts on the wall and the ground, respectively:
- \( -F_{\text{ladder on wall}} \)
- \( -F_{\text{ladder on ground}} \)
So the answer would be:
\( F_{\text{wall on ladder}} \) and \( F_{\text{ground on ladder}} \).