The given system of equations in augmented matrix form is
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\-6&1&2&4&-12\\1&-3&-3&5&-20\\-2&5&6&0&12\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C-6%261%262%264%26-12%5C%5C1%26-3%26-3%265%26-20%5C%5C-2%265%266%260%2612%5Cend%7Barray%7D%5Cright%5D)
If you need to solve this, first get the matrix in RREF:
- Add 2(row 1) to row 2, row 1 to -3(row 3), and 2(row 1) to 3(row 4):
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&5&-6&8&-58\\0&11&5&-13&37\\0&19&10&4&-10\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%265%26-6%268%26-58%5C%5C0%2611%265%26-13%2637%5C%5C0%2619%2610%264%26-10%5Cend%7Barray%7D%5Cright%5D)
- Add 11(row 2) to -5(row 3), and 19(row 1) to -5(row 4):
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&5&-6&8&-58\\0&0&-91&153&-823\\0&0&-164&132&-1052\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%265%26-6%268%26-58%5C%5C0%260%26-91%26153%26-823%5C%5C0%260%26-164%26132%26-1052%5Cend%7Barray%7D%5Cright%5D)
- Add 164(row 3) to -91(row 4):
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&5&-6&8&-58\\0&0&-91&153&-823\\0&0&0&13080&-39240\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%265%26-6%268%26-58%5C%5C0%260%26-91%26153%26-823%5C%5C0%260%260%2613080%26-39240%5Cend%7Barray%7D%5Cright%5D)
- Multiply row 4 by 1/13080:
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&5&-6&8&-58\\0&0&-91&153&-823\\0&0&0&1&-3\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%265%26-6%268%26-58%5C%5C0%260%26-91%26153%26-823%5C%5C0%260%260%261%26-3%5Cend%7Barray%7D%5Cright%5D)
- Add -153(row 4) to row 3:
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&5&-6&8&-58\\0&0&-91&0&-364\\0&0&0&1&-3\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%265%26-6%268%26-58%5C%5C0%260%26-91%260%26-364%5C%5C0%260%260%261%26-3%5Cend%7Barray%7D%5Cright%5D)
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&5&-6&8&-58\\0&0&1&0&4\\0&0&0&1&-3\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%265%26-6%268%26-58%5C%5C0%260%261%260%264%5C%5C0%260%260%261%26-3%5Cend%7Barray%7D%5Cright%5D)
- Add 6(row 3) and -8(row 4) to row 2:
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&5&0&0&-10\\0&0&1&0&4\\0&0&0&1&-3\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%265%260%260%26-10%5C%5C0%260%261%260%264%5C%5C0%260%260%261%26-3%5Cend%7Barray%7D%5Cright%5D)
![\left[\begin{array}{cccc|c}3&2&-4&2&-23\\0&1&0&0&-2\\0&0&1&0&4\\0&0&0&1&-3\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%262%26-4%262%26-23%5C%5C0%261%260%260%26-2%5C%5C0%260%261%260%264%5C%5C0%260%260%261%26-3%5Cend%7Barray%7D%5Cright%5D)
- Add -2(row 2), 4(row 3), and -2(row 4) to row 1:
![\left[\begin{array}{cccc|c}3&0&0&0&3\\0&1&0&0&-2\\0&0&1&0&4\\0&0&0&1&-3\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D3%260%260%260%263%5C%5C0%261%260%260%26-2%5C%5C0%260%261%260%264%5C%5C0%260%260%261%26-3%5Cend%7Barray%7D%5Cright%5D)
![\left[\begin{array}{cccc|c}1&0&0&0&1\\0&1&0&0&-2\\0&0&1&0&4\\0&0&0&1&-3\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7Cc%7D1%260%260%260%261%5C%5C0%261%260%260%26-2%5C%5C0%260%261%260%264%5C%5C0%260%260%261%26-3%5Cend%7Barray%7D%5Cright%5D)
So the solution to this system is
.
Answer:
d. 9x + 63 and 63 square feet
Step-by-step explanation:
Given
Original


Extended



Required
Determine an expression and the value of the extended area
First, we calculate the area of the original desk


From the given parameters, we have:
--- area of the new surface
Open bracket

The area of the new surface is the summation of the area of the original desk and the area of the extended portion (E)
So:

Make E the subject



Hence, the area of the extended portion is 63