Answer:
System of equations:

Augmented matrix:
![\left[\begin{array}{cccc}1&2&2&6\\2&1&1&6\\1&1&3&6\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D1%262%262%266%5C%5C2%261%261%266%5C%5C1%261%263%266%5Cend%7Barray%7D%5Cright%5D)
Reduced Row Echelon matrix:
![\left[\begin{array}{cccc}1&2&2&6\\0&1&1&2\\0&0&1&1\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D1%262%262%266%5C%5C0%261%261%262%5C%5C0%260%261%261%5Cend%7Barray%7D%5Cright%5D)
Step-by-step explanation:
Convert the system into an augmented matrix:
![\left[\begin{array}{cccc}1&2&2&6\\2&1&1&6\\1&1&3&6\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D1%262%262%266%5C%5C2%261%261%266%5C%5C1%261%263%266%5Cend%7Barray%7D%5Cright%5D)
For notation, R_n is the new nth row and r_n the unchanged one.
1. Operations:

Resulting matrix:
![\left[\begin{array}{cccc}1&2&2&6\\0&-3&-3&-6\\0&-1&1&0\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D1%262%262%266%5C%5C0%26-3%26-3%26-6%5C%5C0%26-1%261%260%5Cend%7Barray%7D%5Cright%5D)
2. Operations:

Resulting matrix:
![\left[\begin{array}{cccc}1&2&2&6\\0&1&1&2\\0&-1&1&0\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D1%262%262%266%5C%5C0%261%261%262%5C%5C0%26-1%261%260%5Cend%7Barray%7D%5Cright%5D)
3. Operations:

Resulting matrix:
![\left[\begin{array}{cccc}1&2&2&6\\0&1&1&2\\0&0&2&2\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D1%262%262%266%5C%5C0%261%261%262%5C%5C0%260%262%262%5Cend%7Barray%7D%5Cright%5D)
4. Operations:

Resulting matrix:
![\left[\begin{array}{cccc}1&2&2&6\\0&1&1&2\\0&0&1&1\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D1%262%262%266%5C%5C0%261%261%262%5C%5C0%260%261%261%5Cend%7Barray%7D%5Cright%5D)
Answer:
13
Step-by-step explanation:
All the lengths in triangle ADE are twice those in similar triangle ABC. So ...
x-1 = 2(6)
x = 13
Answer:
Limits for B scores
( 79,2 ; 92 )
Step-by-step explanation:
The interval we are looking for is between 6 % and 59%
p₁ = 6 % p₁ = 0,06
As this point is at the right tail of the bell we better look for
p = 1- 0,06 p = 0,94
In z-table z score for 0,94062 is: z₁ = 1,56 ( 0,94062 ≈ 0,94 )
Doing the same to find z₂ score for 59% or 0,59
In z-table again
p = 0,59
z₂ = 0,023
Now we know
1,56 * σ = x₁ - 79
1,56*8,4 + 79 = x₁
x₁ = 92,10 or x₁ = 92
And
0,023*8,4 + 79 = x₂
x₂ = 79,19 or x₂ = 79,2
Exact value of that equation is 4