This is a basic MATLAB operation. It is for instructional purposes.
You may already know how to find the logical indices of the elements of a vector that meet your criteria.
This exercise is for finding the index of indices that meet your criteria. The difference is this:
vec = [11 22 33 44]; thresh = 25; vi = (vec > thresh)
0 0 1 1
What we are looking for now is how to get the values
Because those are the indices where the binary comparison is true.
Check out find.
Given a vector, vec, return the indices where vec is greater than scalar, thresh.