There are two steps down,
A There are two steps on the right.
So choose two of the four steps to the right, C 4 2 = 6.
Enumeration: lower right, lower right, lower right, lower right, lower right, lower right, lower right, lower right, lower right.
Second photo,
There are three steps down,
A There are four steps on the right.
A * * * is seven steps, choose three steps down, C 7 3=35.
There are too many such cases, so I won't list them one by one, but you can have a try.
The third picture,
There are five steps down,
A There are eight steps on the right.
A *** 13 step, select 5 steps down, C 13 5= 1287.
See the pattern?