Answer: 
<u>Step-by-step explanation:</u>
Given: cos x =
, x is in Quadrant 4
Use Pythagorean Theorem to find sin x:
8² + y² = 17²
y² = 17² - 8²
y² = 289 - 64
y² = 225
y = 15
→ sin x = 
Use the double angle formula to find cos (2x):

Quick note: Since Riona wants to sell like 90 or 100 the answer I got was for 95.
I hope this helps you but the answer would be approximately about 83125.
Answer:
$1.94
Step-by-step explanation:
Cost of 3 folders = $2.91
We need to find the cost of 2 folders.
First we will find the cost of 1 folder
1 folder = $2.91/3 = $0.97
To find the cost of 2 folders, multiply $0.97 and 2
2 folders = $0.97 × 2
= $1.94
Hence, the cost of 2 olders is $1.94.
4.08, or 4 2/25 :) hope this helps