There are 680 combinations of four teachers include Mrs. Vera(only)
The given parameters are
Teachers, n = 18
Selected teachers. r = 4
The selection must include Mrs. Vera.
So, the remaining parameters are:
Teachers, n = 17
Selected teachers. r = 3
The combination is then calculated as:
Ways = nCr
This gives
Ways = 17C3
Apply the combination formula
Ways = 17!/(14!3!)
Evaluate the expression
Ways = 680
Hence, there are 680 combinations of four teachers include Mrs. Vera(only)
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