D) 36x^2-81
both 36x^2 and -81 are perfect squares
difference means subtraction
For this case what you must do is the following rule of three:
50 ---> 100
80 ----> x
We clear x:
x = (80/50) * (100)
x = 160%
160-100 = 60%
Answer:
toni added 60% of the original value for his sale price
Answer:
Step-by-step explanation:

Let us draw a picture to make the things more clear.
Attached is the image.
We have been given that

Therefore, we have

Now, in triangle bcd, we have

Now, in triangle acb, we have

Thus, ad is 15 cm.
You can see the polygon in the attached figure.
It's a trapezoid, so it's not equilateral, nor regular.