By the time Christopher Langan ____ (be) three years old, he _____ (teach) himself to read.
was/ had taught
By the time chess player Judit Polgár _____ (be) 16, she _____ (become) an international Grandmaster at chess.
was/ had become
Akrit Jaswal _____ (manage) to perform hsi first operation at 3 because he _____ (read) books about it.
managed/ had read