in DNA strands the complimentary bases go A=T and C=G and vice versa. so whenever you come across base pairs and it asks for the complimentary DNA sequence then you plug in a new sequence that corresponds with the old one. Just know that when dealing with RNA it is slightly different. if you ever want me to explain that then lmk whenever. I'll try and get back to you. I really hope this makes sense and that i was able to help you!!!! have a great day/night.
