Arrangements of BOOLAHUBBOO with B's first

Consider all distinct rearrangements of the letters of $\text{BOOLAHUBBOO}$. In how many of them does every $B$ come before every $O$?

$7920$. Choose the $7$ positions for the three B's and four O's in $\binom{11}{7}$ ways; only one filling (BBBOOOO) has all B's first. The remaining four distinct letters L, A, H, U fill the other spots in $4!$ ways, so $330\cdot24=7920$.