Abstract: A network-theoretic approach for determining the complexity of a graph is proposed. This approach is based on the relationship between the linear algebra (theory of determinants) and the graph theory. In this paper we contribute a new algebraic method to derive simple formulas of the complexity of some new networks using linear algebra. We apply this method to derive the explicit formulas for the friendship network and the subdivision of friendship graph . We also calculate their spanning trees entropy and compare it between them. Finally, we introduce an open problem "Any improvement for calculating of the determinant in linear algebra, we can investigate this improvement as a new method to determine the number of spanning tree for a given graph.