The property applied is the associative property
<h3>Algebraic properties</h3>
There are several algebraic properties in mathematics; each of which have their own applications
Some of these properties are:
- Commutative
- Distributive
- Associative
- Identity
The mathematical expression is given as:

And it is calculated as follows:


The property applied above is the associative property
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The value of x when y is 14.4 is 5.
It is given that
y ∝ 1/x
y = k/x....(1)
Where k is a constant of proportionality
<h3>What is the constant of proportionality?</h3>
The constant of proportionality is the ratio that relates two given values.
When y =6, x=12
Means, 6 = k/12
k = 72
Putting the value of k in equation (1)
y = 72/ x
14.4 = 72/ x
x = 5
Therefore, The value of x when y is 14.4 is 5.
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It would be B I believe!!