To generate the complementary sequence we need to remember how bases are paired, as well the fact that meanwhile one strand in 5' to 3' the complementary goes in the opposite direction 3' to 5'
Bases are paired Adenine to Thymine, and Guanine to Cytosine. So now we can proceed to make the complementary chain.
5'- AGATCCG-3' Leading
3'- TCTAGGC-5' Complementary