How long did it take the album "Fleetwood Mac" (1975) to hit #1?

Fleetwood Mac was basically a revolving door of musicians until 1975, when everything finally clicked. The self-titled album they released that July introduced the world to the magic that happened when Lindsey Buckingham agreed to join on the condition that his music partner and girlfriend, Stevie Nicks, be included. The record would eventually climb all the way to the top of the charts, but Rome wasn't built in a day, and neither was a number one album. How long did it take "Fleetwood Mac" to reach number one on the Billboard 200?