in the given question is asking about no. of vertices in the tree as we know that
e(edge)=n(no. of vertice)-1
using the handshake theorem sum of degree = 2|e|
2*4+1*3+1*2+(n-(2+1+1))*1=2|n-1|
{ (n-(2+1+1))*1 ------> remaining other vertices }
8+3+2+n-4=2n-2
8+3+2+2-4=2n-n
11=n
two vertices of degree 4, one vertex of 3 and one vertex of degree ‘2’. If all other vertices have degree 1