Final answer:
The sequence complementary to AAG on one strand of DNA's double helix is TTC on the other strand, following the base-pairing rules.
Step-by-step explanation:
The double helix structure of DNA consists of two strands that are antiparallel and complementary to each other. According to the base-pairing rules, adenine (A) always pairs with thymine (T), while guanine (G) pairs with cytosine (C). Therefore, if one side of the DNA double helix has the sequence AAG, the other side would have the sequence TTC because each adenine on the original strand pairs with a thymine on the complementary strand, and each guanine pairs with a cytosine.