First, we need to convert the mixed numbers into improper fractions:
9цел12/25 = (259 + 12)/25 = 237/25
8цел16/25 = (258 + 16)/25 = 216/25
4цел17/25 = (25*4 + 17)/25 = 117/25

Now, the expression becomes:
(237/25 - 216/25) + 117/25
= (21/25) + 117/25
= 138/25

Therefore, the result is 5цел13/25.