A cat sitting on the edge of a straight river bank spots a bird sitting in a tree directly across the river and on the river's edge. The angle of elevation from the cat to the bird is 15 degrees. The cat then moves 25m along the river bank, and now spots the same bird at an angle elevation of 13 degrees. How high is the tree?

I have tried to solve this using simultaneous equations and get an answer of 42m which is wrong. Can you help please??