The objective of the game is to capture the Knight with the Rook, according to the number of moves allows for each example. For instance, in this particular case, we need to capture the knight in two steps.
The Rook is the only pieces that is going to move, but we need to move the Rook on a safe square, not a square that can be captured by an opponent piece.
In this case, the moves are 1.Rf6 and 2.Rxb6 (see diagram A below), but trying with 1.Rb1 is not going to work because the black Bishop on e4 is going to capture the Rook (see diagram B).
In other examples the Rook will have to move 3 or 4 times (on safe squares) to catch the Knight, making the problems more difficult.
White Rook moves and captures the Knight in 3 consecutive moves.
White Rook moves and captures the Knight in 2 consecutive moves.
"Capturing the Knight"
It is important to clarify that this game is not designed to help chess players to calculate better.
The objective of the game is to help students without deep chess knowledge to develop critical thinking skills, calculation, planning, strategically thinking, etc.
Assuming that all students in the world would like to learn and practice chess in competitions, this games probably would be not necessary, but as we all know, this is, unfortunately, not the case. As you notice, to play this game, you just need to know how to move the chess pieces.
This is one of the games that I play with my students during center time, and I will be posting some exercises for the public use. Here, I leave you one more exercise for you to practice.
Thank you so much!
Ramón Miguel Lorente Pupo.