Answer:
The phase that describes an unknown or chargeable quantity is the "variable" phase.
In mathematics and other quantitative fields, a variable represents an unknown or changing value. It is a symbol or letter that can take on different values or quantities.
Variables are often used to represent unknown quantities in equations or mathematical models. They allow us to solve problems and find the value of the unknown quantity.
For example, in the equation 3x + 5 = 20, the variable "x" represents the unknown quantity. By solving the equation, we can determine the value of "x" and find out what the unknown quantity is.
In the context of chargeable quantities, a variable can represent a cost, price, or fee that varies depending on certain factors. For instance, the cost of a phone bill may be represented by the variable "c," which can change from month to month based on factors such as usage or additional charges.
Therefore, when we encounter an unknown or chargeable quantity, we can describe it as a variable, as it represents a value that is subject to change or needs to be determined.