P({1,3,5}) = 0.9P({2,4,6}) and their sum must be 1. It means
P({1,3,5}) + P({2,4,6}) = 1 .... Now substitute the values of P({1,3,5}) and P({2,4,6})..... took lot of time to understand this ... seriously some of ur explanations take lot of time to understand ....