The sides of the dna molecule, the rails of the ladder, are composed of what

Phosphates and Sugars.

Explanation:

The strands are nucleotides and are connected by a pattern of phosphates and sugars.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)