First Round

Annemiek and Bart each have a note on which they have written three different positive integers. It appears that there is exactly one number that is on both their notes. Moreover, if you add any two different numbers from Annemiek's note, you get one of the numbers on Bart's note. One of the numbers on Annemiek's note is her favourite number, and if you multiply it by $3$, you get one of the numbers on Bart's note. Bart's note contains the number $25$, his favourite number. What is Annemiek's favourite number?