
Step-by-step explanation:
The elements of matrices are represented in the form

Here r is the row number and c is the column number.
Given matrix is:
![A = \left[\begin{array}{ccc}3&6&9\\2&4&8\end{array}\right]](https://tex.z-dn.net/?f=A%20%3D%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D3%266%269%5C%5C2%264%268%5Cend%7Barray%7D%5Cright%5D)
The elements of matrix will be represented by a_{r,c}
We have to find 
Which means that the first row and third column.
The first row is: 3 6 9 and the element in third column is: 9
So,

Keywords: Matrices, Elements
Learn more about matrices at:
#LearnwithBrainly
D=m/v so d=50/10=5
The density is 5g/ml
It might be ml^3 (5g/ml^3) but I don’t remember
It’s B because I got it right
For the first one it’s subtraction property of equality