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\frac{11}{15},\frac56,\frac34, \frac12, \frac35, \frac14
Why?
Starting from the beginning
Start with a denominator which can divide 75 without a remainder. The options are \frac{11}{15} or \frac35. Here you have to choose one and see if it works. This tree shows all of the possibilities:
Starting from the end
On the last day, the fraction he wants to keep needs to be \frac12 or \frac14, or a fraction with the numerator as 2. This is because the number of peaches has to be 2 (because he eats 1), but if the numerator is larger than 2, then there will be more than 2 peaches.
This tree shows the possibilities working from the end: