The sqaure of 9 less than a number is 3 less than the number

n:  {7, 12}

Step-by-step explanation:

(n - 9)^2 = n - 3, or

n² - 18n + 81 = n - 3

Rewriting this into the form of a quadratic, we get:

n² - 19n + 84 = 0, or

(n - 7)(n - 12) = 0

Then n:  {7, 12}

linear pair postulates

it would open into a square depending on the type of envelope i’m not sure about the second part