what is the value of x?

Question

Thomas wants to invite Madeline to a party. He has an 80% chance of bumping into her at school. Otherwise, he’ll call her on the phone. If he talks to her at school, he’s 90% likely to ask her to a party. However, he’s only 60% likely to ask her over the phone.

This is the tree diagram that represents the probability of Thomas inviting Madeline to a party.

What is the value of X?

Answer 1

x + 0.6 = 1; x = 1 - 0.6 = 0.4