85 x 3 = 255
first 2 test grades were 81 and 86:
81 + 86 = 167
Need to find the 3rd to have exact average 85:
255 - 167 = 88
So her 3rd test needs to make 88 to make average of 85
Double check: 81 + 86 + 88 = 255 = 85 + 85 + 85
Answer:

Step-by-step explanation:
Here the logarithm has base 2

Let



Now, take logarithm to the base 10

So, 
The IQR of the data set is choice C: 9.
To find the IQR, you have to first put the numbers in order.
The order is: 10 12 15 17 19 21 23
The IQR is the difference between the first quartile and the third quartile.
Those values are 12 and 21.
21 - 12 = 9
Answer: -1/18 im pretty sure
Step-by-step explanation: Find the exact value using trigonometric identities.
Answer:
2.5
Step-by-step explanation: