Using an exponential function, it is found that Mary's initial investment was of $3,030.
<h3>What is an exponential function?</h3>
An exponential function is modeled by:
.
In which:
Her investment model, in thousands of dollars, is:

Then a = 3.03, since we measure the amount in thousands of dollars, Mary's initial investment was of $3,030.
More can be learned about exponential functions at brainly.com/question/25537936
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The image is kinda blurry, but from what I can gather, the notation in the attachment means
![p_X[x_k]\equiv\mathbb P(X=k)=\begin{cases}(1-p)^{k-1}p&\text{for }k=1,2,\ldots\\0&\text{otherwise}\end{cases}](https://tex.z-dn.net/?f=p_X%5Bx_k%5D%5Cequiv%5Cmathbb%20P%28X%3Dk%29%3D%5Cbegin%7Bcases%7D%281-p%29%5E%7Bk-1%7Dp%26%5Ctext%7Bfor%20%7Dk%3D1%2C2%2C%5Cldots%5C%5C0%26%5Ctext%7Botherwise%7D%5Cend%7Bcases%7D)
Then
a)
![p_X[x_k\le4]\equiv\mathbb P(X\le4)=\mathbb P(X=1)+\mathbb P(X=2)+\mathbb P(X=3)+\mathbb P(X=4)](https://tex.z-dn.net/?f=p_X%5Bx_k%5Cle4%5D%5Cequiv%5Cmathbb%20P%28X%5Cle4%29%3D%5Cmathbb%20P%28X%3D1%29%2B%5Cmathbb%20P%28X%3D2%29%2B%5Cmathbb%20P%28X%3D3%29%2B%5Cmathbb%20P%28X%3D4%29)
b)

c)
Combine like terms
-6x² + (-x²) = -6x² - x² = -7x²
-7x² + 15x + 4 is your answer
hope this helps
We shall see how much percentage of the original price was the price discounted and it will show the percentage decreased
325x/100=123.50
325x=12350
X=12350/325
X=38
hope u found this answer helpful