In the first series, the summation applies to the whole (2n+3) inside
the parentheses, so the 3 gets summed up 5 times.
But in the second one, the summation only applies to the 2n , so
the 3 is only added after the summation is finished.
The difference between five 3s the first time and one 3 the second time
is your 12 .
Answer:

Step-by-step explanation:

Don't mind the 
The vertical line test is when you put vertical lines down the graph and if the point does not touch the line more than once, it passes and represents a function.
300 is 10 times as much as 30.
because if you do 30 x 10 you get 300
The probability is 0.8997.
We will use a z-score to answer this question. z-scores are given by the formula

With our information, we have

Looking this up in a z-table (http://www.z-table.com) we see that the area to the left of this (everything less than, up to this value) is 0.8997.