The solution for this question is confusing.
The up move for the binomial tree is 15% and the down move is 20%.
With an initial value of 30, the first up move is 34.50 but the down move is 25.
How is the down move 25? I would think the up move would be 30 * (1.15) = 34.50 and the down move 30 * (1-0.20) = 24