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
F(x,y)=8x+y
This means, f is a function where we plug in pairs of numbers.
then, f calculates the first number times 8, to which it then adds the second number we plugged.
let's calculate f for the vertices:
f(0,0)=8*0+0=0+0=0
f(4, 0)=8*4+0=32+0=32
f(3, 5)=8*3+5=24+5=29
f(0, 5)=8*0+5=0+5=5
the maximum value of f is 32
the minimum value of f is 0
All you do is add them all together...
20 + 11.4 + 11.4 + 4.5 + 4.5 + 0.45 + 0.45 + 0.45 + 0.45 = 53.6Kg
(note that 0.45 is 450g in Kg, When adding things such as weight or length you want to make sure that they are all in the same unit)