What is the complementary strand of dna for this strand of dna? actgctagctgactta?

Complementary strands of DNA have opposing matching nucleotides following base pair rules:

A - > T (U in RNA)

G - > C

With these in mind, let us copy your strand of DNA followed by the complementary strand underneath:

Original: A C T G C T A G C T G A C T T A

Complementary: T G A C G A T C G A C T G A A T

This is the sequence for your complementary strand of DNA.