There are: . possible outcomes.A school principal needs to employ 9 staff members.
There are 4 lab assistants and 10 science teachers.
How many ways can he select 9 staff members if he needs at least one lab assistant?
The opposite of "at least one LA" is "no LA's" . . . that is, "all ST's."
. . There are: . ways to choose all ST's.
Therefore, there are: . ways to have at least one LA.