Answer:

Step-by-step explanation:
![S= \frac{n}{2 [2a + (n - 1)d]}](https://tex.z-dn.net/?f=S%3D%20%5Cfrac%7Bn%7D%7B2%20%5B2a%20%2B%20%28n%20-%201%29d%5D%7D)
Simplifying the fraction by multiplying d into the (n-1) term,
![s=\frac{n}{2 [2a + (n - 1)d] } = \frac{n}{2[2a + dn - d] }](https://tex.z-dn.net/?f=s%3D%5Cfrac%7Bn%7D%7B2%20%5B2a%20%2B%20%28n%20-%201%29d%5D%20%7D%20%3D%20%5Cfrac%7Bn%7D%7B2%5B2a%20%2B%20dn%20-%20d%5D%20%7D)
Simplifying the fraction by multiplying 2 throughout,

Multiply
on both sides

Cancel the
on the right hand side

Multiply s to the terms,

Move
to the right hand side by subtracting
on both sides

On the right hand side of the equation, take out 

Divide Left hand side by
,

Step-by-step explanation:
sum of all angles = 360
7x-4 = 360
7x= 364
x = 52
angle j = 150
angle k = 62
angle m = 100
Answer: 1:3
Step-by-step explanation: for 4 toads you have 12 frogs so the ratio is 4 to 12. But you can simplif, divide each side by 4 so it’s 1 to 3
The general equation for a circle is:

where (h,k) is center of circle
r = radius
For this example, from the graph you see the center is at (0,-3) and radius is 2.
h = 0, k = -3, r = 2
Sub into general equation:
Answer:
1) 1 element
2) 13 elements
3) 22 elements
4) 40 elements
Step-by-step explanation:
1) Only one element will have no tails: the event that all the coins are heads.
2) 13 elements will have exactly one tile. Basically you have one element in each position that you can put a tail in.
3) There are
elements that have exactly 2 tails. From those elements we have to remove the only element that starts and ends with a tail and in the middle it has heads only and the elements that starts and ends with a head and in the 11 remaining coins there are exactly 2 tails. For the last case, there are
possibilities, thus, the total amount of elements with one tile in the border and another one in the middle is 78-55-1 = 22
4) We can have:
- A pair at the start/end and another tail in the middle (this includes a triple at the start/end)
- One tail at the start/end and a pair in the middle (with heads next to the tail at the start/end)
For the first possibility there are 2 * 11 = 22 possibilities (first decide if the pair starts or ends and then select the remaining tail)
For the second possibility, we have 2*9 = 18 possibilities (first, select if there is a tail at the end or at the start, then put a head next to it and on the other extreme, for the remaining 10 coins, there are 9 possibilities to select 2 cosecutive ones to be tails).
This gives us a total of 18+22 = 40 possibilities.