Another math thing that seems hard, but can be looked at in an easy way:

Quick rule... to just represent the value of a matrix, enclose the elements (technically, they're "entities") in brackets. To say "the determinant of," enclose the elements in two big pipes.

+- -+ | |
|a b c| |a b c|
det |d e f| = |d e f|
|g h i| |g h i|
+- -+ | |

Finding the determinant of any matrix just requires you to start at the first element of the first row, and multiply it by all the elements diagonally below and to the right of it. Do this for every element in the row, then add the results together. Next, start at the first element of the bottom row, and multiply it by every element diagonally above and to the right of it, and continue for each element in the row, adding the results together. Subtract this result from the total you got before. To make the process easier ("What's diagonally above i? It's in the last column!") you must wrap around the matrix, or copy the elements to be on the right side of the matrix:

| |
|a b c|a b <- these last two columns
A= |d e f|d e placed for visual
|g h i|g h reference
| |
|A|=((a*e*i)+(b*f*g)+(c*d*h))-((g*e*c)+(h*f*a)+(i*d*b))
| |
|1 3 4|1 3
B= |5 2 9|5 2
|6 1 2|6 1
| |

1*2*2=4

3*9*6=162

4*5*1=20

4+162+20=186

6*2*4=48

1*9*1=9

2*5*3=30

48+9+30=87

186-87=99

|B|=99

The more compact way of finding out the determinant is:

|B|=((1*2*2)+(3*9*6)+(4*5*1))-((6*2*4)+(1*9*1)+(2*5*3))

|B|=(4+162+20)-(48+9+30)

|B|=186-87

|B|=99