I can't see it clearly the questions ?
The order of mathematical operation is MDAS.
M - multiplication
D - division
A - addition
S - subtraction
3 - 3 x 6 + 2
Multiplication : 3 x 6 = 18
Division: none
Addition : + 3 + 2 = 5 (combine positive numbers)
Subtraction : 5 - 18 = -13
3 - 18 + 2 = -13
The property that is being described in the statement "The sum of the components of anything equals the whole thing" would be the Partition Postulate. It is simply the whole is equal to the sum of its parts. For instance we have a line where it contains points W, X, Y and Z, then WX + XY + YZ = WZ.
3^2+3^2=c^2
18=c^2
c=3sqrt2
Or 4.24 if you need a decimal answer
Octogon
sides=4
draw lines from the outside angles to the center so they form 8 equal triangle sections
find the area of each triangle and multiply by 8
area of triangle=1/2 base times height
base=4
the height is the distance from the center of one side of the octogon, to the center=5
so area=4 times 1/2 times 5=4 times 5=10
8 triangles so 8 times 10=80
the answer is 80cm^2
the diagram included below shows area for a pentagon