Answer:
 or
   or    (depending on your teacher's format preference)
   (depending on your teacher's format preference)
Step-by-step explanation:
<h3><u>
Proportionality background</u></h3>
Proportionality is sometimes called "variation".   (ex. " 'y' varies inversely as 'x' ")
There are two main types of proportionality/variation:
- Direct
- Inverse.
Every proportionality, regardless of whether it is direct or inverse, will have a constant of proportionality (I'm going to call it "k").
Below are several different examples of both types of proportionality, and how they might be stated in words:
 y is directly proportional to x y is directly proportional to x
 y is directly proportional to x squared y is directly proportional to x squared
 y is directly proportional to x cubed y is directly proportional to x cubed
 y is directly proportional to the square root of x y is directly proportional to the square root of x
 y is inversely proportional to x y is inversely proportional to x
 y is inversely proportional to x squared y is inversely proportional to x squared
From these examples, we see that two things:
- things that are <u>directly proportional</u> -- the thing is <u>multipli</u>ed to the constant of proportionality "k"
- things that are <u>inversely proportional</u> -- the thing is <u>divide</u>d from the constant of proportionality "k".
<h3><u>
Looking at our question</u></h3>
In our question, y is inversely proportional to x, so the equation we're looking at is the following  .
.
It isn't yet clear what the constant of proportionality "k" is for this situation, but we are given enough information to solve for it:  "When y=12, x=5."
We can substitute this known relationship pair, and find the "k" that relates this pair of numbers:
<h3><u>
Solving for k, and finding the general equation</u></h3>
General Inverse variation equation...

Substituting known values...

Multiplying both sides by 5...

Simplifying/arithmetic...

So, for our situation, k=60.  So the inverse proportionality relationship equation for this situation is  .
.
The way your question is phrased, they may prefer the form: 