I believe the answer would be 300. One eighth of the class would be 100 and 1/2 of the class would be 400. 800-(400+100)=300. Hope this helped!
Suppose

is the number of possible combinations for a suitcase with a lock consisting of

wheels. If you added one more wheel onto the lock, there would only be 9 allowed possible digits you can use for the new wheel. This means the number of possible combinations for

wheels, or

is given recursively by the formula

starting with

(because you can start the combination with any one of the ten available digits 0 through 9).
For example, if the combination for a 3-wheel lock is 282, then a 4-wheel lock can be any one of 2820, 2821, 2823, ..., 2829 (nine possibilities depending on the second-to-last digit).
By substitution, you have

This means a lock with 55 wheels will have

possible combinations (a number with 53 digits).
Answer:
119 R5
divide divide divide divide
The way it is written, none of them.

The "a"s cancel out.
The expression that does not represent the sum of n and 6 is 6n