Observe the given graph(rectangular+traingle+hexagon)
Spanning tree contains no cycles. & connects all vertices.
for rectangular area=> select 3 out of 5 edges & remove 2 traingular cycle = 5c3-2 = 8
for traingular area=> select 2 out of 3 edges = 3c2 = 3
for hexagonal area=> select 5 out of 7 edges & remove cycles(formed by 4 edges with any 1 edge out of remaining 3 edges) = 7c5-2(3c1) = 21-6 = 15.
so, total possible spanning tree = 8*3*15= 360.