Where’s the triangle, isn’t there supposed to be a picture with the question
can you make the pic little more clear if you can :)
Answer:
The probability is 
Step-by-step explanation:
We can divide the amount of favourable cases by the total amount of cases.
The total amount of cases is the total amount of ways to put 8 rooks on a chessboard. Since a chessboard has 64 squares, this number is the combinatorial number of 64 with 8,
For a favourable case, you need one rook on each column, and for each column the correspondent rook should be in a diferent row than the rest of the rooks. A favourable case can be represented by a bijective function
with A = {1,2,3,4,5,6,7,8}. f(i) = j represents that the rook located in the column i is located in the row j.
Thus, the total of favourable cases is equal to the total amount of bijective functions between a set of 8 elements. This amount is 8!, because we have 8 possibilities for the first column, 7 for the second one, 6 on the third one, and so on.
We can conclude that the probability for 8 rooks not being able to capture themselves is

the vertical line test is a graphical way to determine whether or not the graph is a function of x
if you can draw a vertical line on a graph and cross the graph at least 2 times, the graph is not a function
a function will have 1 y value for every x value, therefore, if we can draw a vertical line (x=c, a constant) that intersects the curve at more than 1 point, then that point where it intersects at more than 1 point is where 1 value of x coresponds to more than 1 value of y and is therefore not a function