Based on the calculations, the unknown number is equal to 
- Let the unknown number be x.
<h3>How to find an
unknown number:</h3>
Translate the word problem into an algebraic expression, we have;
Adding 21 to the unknown number:

Multiplying the result by 3:

84 more than two-thirds of the unknown number:

Equating the equations, we have:

Cross-multiplying, we have:

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Answer:
the answer is D
Step-by-step explanation:
Answer:
This assignment can be made in 1365 ways.
Step-by-step explanation:
The order in which the shifts are assigned is not important. For example, employees A, B, C, D and D,C,B,A being assigned is the same thing. So, we use the combinations formula to solve this question.
Combinations Formula:
is the number of different combinations of x objects from a set of n elements, given by the following formula.

In this question:
Assignment of 4 employees, from a set of 15. So
