ANSWER
24
EXPLANATION
For a matrix A of order n×n, the cofactor
of element
is defined to be

is the minor of element
equal to the determinant of the matrix we get by taking matrix A and deleting row i and column j.
Here, we have

M₁₁ is the determinant of the matrix that is matrix A with row 1 and column 1 removed. The bold entries are the row and the column we delete.

Since the determinant of a 2×2 matrix is

it follows that

so 
Answer:
258
Step-by-step explanation:
Set up the two equations needed (x is the adult tickets and y is the student tickets)
x+y=372
6x+2y=1776
Solve by elimination
-2(x+y=372)
=-2x-2y=-744
Cancel like figures:
-2x-2y=-744
6x+2y=1776
= 4x=1032
x=258
R=xa+xb, r-xa=xb, b=r-xa/x
Answer:
3 triangles
Step-by-step explanation:
Perimeter of triangle = a + b + c
Given that :
P = 12
and a, b, c are natural numbers
Let :
Side A = a
Side B = b
Side C = 12 - (a + b)
Side A + side B > side C - - - (condition 1)
a + b > 12 - (a + b)
a + b > 12 - a - b
a + a + b + b > 12
2a + 2b > 12
2(a + b) > 12
a + b > 6
Side A - side B < side C
a - b < 12 - (a + b)
a - b + a + b < 12
2a < 12
a < 6
b < 6 (arbitrary point)
Going by the Constraint above :
The only three possibilities are :
(2, 5, 5)
(3, 4, 5)
(4, 4, 4)
Total number of triangle = 3
Equilateral triangle (all 3 sides equal) = (4, 4, 4) = 1
Isosceles triangle (only 2 sides equal) = (2, 5, 5) = 1