![\left[ \begin{matrix} 2 & a \\ -1 & -2 \end{matrix} \right] + \left[ \begin{matrix} b & 4 \\ -2 & 1 \end{matrix} \right]](https://tex.z-dn.net/?f=%5Cleft%5B%20%5Cbegin%7Bmatrix%7D%202%20%26%20a%20%5C%5C%20-1%20%26%20-2%20%5Cend%7Bmatrix%7D%20%5Cright%5D%20%2B%20%5Cleft%5B%20%5Cbegin%7Bmatrix%7D%20b%20%26%204%20%5C%5C%20-2%20%26%201%20%5Cend%7Bmatrix%7D%20%5Cright%5D)
This addition of matrices can be combined into one matrix.
To add matrices, add the corresponding components of each matrix.
After adding, we'll have the following
![\left[ \begin{matrix} 2+b & a+4 \\ -3 & -1 \end{matrix} \right]](https://tex.z-dn.net/?f=%20%5Cleft%5B%20%5Cbegin%7Bmatrix%7D%202%2Bb%20%26%20a%2B4%20%5C%5C%20-3%20%26%20-1%20%5Cend%7Bmatrix%7D%20%5Cright%5D%20)
This matrix should be equal to the matrix on the right-hand side of the equation. This means that each corresponding component of this matrix and the other matrix should be equivalent.
This means that

AND

Solving these one-step equations will give the values of a = -4 and b = -1. That's answer choice D.
Answer: 240
Step-by-step explanation:
Let the missing number be represented by p
5% of p = 12, where 5% = 5/100
Therefore, we can rewrite the expression as:
5/100 x p = 12
= 0.05p = 12
Divide both sides by 0.05 to get the value of p
0.05p/0.05 = 12/0.05
p = 240
Therefore, 5% of 240 = 12