First, let's find angle A.
The angles of a triangle always add up to 180 degrees.
A + B + C = 180
A + 45 + 55 = 180
A + 100 = 180
A = 80 degrees
The longest side is always opposite the largest angle.
Since A is the largest angle, the longest side is BC.
The next largest angle is C, and the next longest side is AB.
And the smallest angle B gives us the shortest side AC.
Therefore, your answer would be BC, AB, AC.