Answer: i inserted two just incase but tell me if i am wrong
Step-by-step explanation:
A matrix is diagonal if

In other words, you want non-zero elements only when the indices of the row and the column are the same: the first element of the first row must be non zero, the second element of the second row must be non-zero, and so on. All other elements must be zero.
I think it’s 20d-$12
Hope this helps!
Step 1: Add up the ages.
32+23+21+38+26=140.
Step 2: Divide answer by the amount of used numbers (5, in this case.)
140/5=28.
Your answer is 28.