The watered-down version of the CRT (which is all you need for stuff like this) tells us that there is a natural map from to , for distinct primes and positive integers , and it is an isomorphism.
To apply the theorem here, we have an element , and we want to find the associated element in . By the euclidean algorithm we can find linear combinations
Each of these equalities corresponds to a value 1, 2 or 3 (mod 8, 25 and 81, respectively). Take the first term in the left of each expression, multiply it by the corresponding value 1/2/3, and then add them all together. We get:
and this is the solution mod . Reducing we get
This equivalence class captures all the solutions to the system by the CRT.