I am studying the book "Elements of Algebraic Topology" written by James R. Munkres. I was stuck in the problem 3.(b). in Section 26 (The Eilenberg Steenrod Axioms), which states that:
if X is the polytope of a simplicial complex K and X_1 and X_2 are the polytopes of subcomplexes of K, and if A is the intersection of X_1 and X_2, then the inclusion (X_1,A) -> (X,X_2) induces a homology isomorphism.
Could I get can any hints to start with?
