The second to last one, looks like a really tall speed bump
Step-by-step explanation:
Consider the provided information.
For the proportion method first set up the equation like this:

Perform the cross multiplication and then solve for the missing part.
For example:
Find 80 percentage of 10.
Step 1: Set up the equation.


Step 2: Perform the cross multiplication

Step 3: Solve for the missing part.


Answer:
$9$
Step-by-step explanation:
Given: Thea enters a positive integer into her calculator, then squares it, then presses the $\textcolor{blue}{\bf\circledast}$ key, then squares the result, then presses the $\textcolor{blue}{\bf\circledast}$ key again such that the calculator displays final number as $243$.
To find: number that Thea originally entered
Solution:
The final number is $243$.
As previously the $\textcolor{blue}{\bf\circledast}$ key was pressed,
the number before $243$ must be $324$.
As previously the number was squared, so the number before $324$ must be $18$.
As previously the $\textcolor{blue}{\bf\circledast}$ key was pressed,
the number before $18$ must be $81$
As previously the number was squared, so the number before $81$ must be $9$.
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