Translation:Their names were in the tenth letter.
I don't know how or where else to report about such a problem, so I'll write it here. While studying this new topic, I had to complete the same tasks twice or even thrice. Was is established intentionally? After all annoying hurdles like "only continious here instead of present", "only our order of words is acceptable here" and etc. it doesn't add enthusiasm to continue learning the course, really.
Because it is neuter.
Singular - jméno bylo (to jméno), plural - jména byla (ta jména). F.e. it is the same with the word auto (car) - auto bylo / auta byla.
byly for neuter plural is used in Common Czech, but not is Standard Czech.