relation on the set corresponding to matrix M I have the following matrix:
$$M = \begin{pmatrix} 1 & 1 & 1\\ 0 & 0 & 1 \\ 0 & 0 & 1 \end{pmatrix}$$

(a) Write the relation on the set {a, b, c} corresponding to M

What exactly do they mean in this case?

They mean that you call rows of your matrix $a, b, c$ and likewise columns, and then two elements are related if the element at the intersection of row of the first and column of the second has a $1.$ For example, in your matrix, $a\sim a,$ since the top left entry is $1.$
