Solve belove question base on Pigeonhole Principle.

Question

A set M=(1,2,......100) is divided into seven subsets with no number in 2 or more subsets. Show that at least one subset either contains four numbers a,b,c, and d such that a+b = c+d or three number p,q and r such that p+q=2r
Solve this problem use Pigeonhole Principle

Answer 1

I want to know how to solve base on the Pigeonhole Principle. Thanks beforehand.

Answer 2

I don't know, but you can use google.

Copy this text in google:

math.stackexchange questions 2865068 any partition of 1 to 100 into seven subsets

When you see list of results you can start from that.