Basically there is a relation between bit rate and baud rate which is:
BaudRate = Bitrate * c * (1/r)
c = Case factor usually = 1 (if nothing mentioned in question)
r = data element per signal element
In manchester signal or differential manchester a data bit is encoded in two signal element so r = 1/2 because for half duration level is up and for half of bit duration its below so two signal element per data element
hence if we substitue the data of r in above we get Baud rate = 2* Bit rate