Let T be a tree with 10 vertices. The sum of the degrees

Let T be a tree with 10 vertices. The sum of the degrees of all the vertices in T is _______.

A tree with 10 vertices has 9 edges.
Such that, n = 10, e = (n – 1) = 10 – 1 = 9
then, ∑degree (V_i) = 2 [edges (E)] = 2 × 9 = 18.