Solving for a variable in an equation means, we are changing the subject of formula of the equation.
The equation of r is: 
The equation is given as:

We start by multiplying both sides by 3

Rewrite as:

Divide both sides by 

Cancel out common factors

Take square roots of both sides

Evaluate the right-hand sides

Make r the subject

Hence, the resulting equating for r is:

Read more about the subject of formulas at:
brainly.com/question/21866313
Start by simplifying each expressions by factoring
















Brainliest? :) (I'd really appreciate if you mark me as brainliest)

Answer:
C. class number and painting preference.
Step-by-step explanation: