Answer:
set mary is x years old, and helen is y years old.
first sentence:x=2y
second one:4(y-8)=x+4
bring x=2y in 4(y-8)=x+4
=>4y-32=2y+4
=>2y=36
=>y=18
=>x=36
mary:36
helen:18
Answer:
<h2>(-10, 2, 6)</h2>
Step-by-step explanation:



The area formula for a parallelogram is base*height=area. Make an equation. You know the area and the height, so plug that into the equation, and you get x*18=396. Solve for x by dividing 396 by 18 and you get 22. So, the base is 22cm.
A set of data has a normal distribution with a mean of 5.1 and a standard deviation of 0.9. Find the percent of data between 4.2 and 5.1.
Answer: The correct option is B) about 34%
Proof:
We have to find 
To find
, we need to use z score formula:
When x = 4.2, we have:


When x = 5.1, we have:


Therefore, we have to find 
Using the standard normal table, we have:
= 

or 34.13%
= 34% approximately
Therefore, the percent of data between 4.2 and 5.1 is about 34%