The answer is C. Compass.
Compass isn't used in the geometric constructions.
you first use distributive property for the multiplication
[(2*4x)-(2*11)]+9=19
8x-22+9=19
Then, you need to leave the variable alone moving all the other numbers with the opposite operation (addition to substraction, substraction to addition, multiplication to division, division to multiplication)
8x=19+22-9
8x=(19+22)-9
8x=41-9
8x=32
Then as 8 and x are multiplying you pass it dividing
x=32/8
x=4
1.
km=kilometers
kilo=1000
1 km=1000meters
so
1/2km= 1/2 times 1000=1000/2=500meters
2. 1/4 km=1000/4=250 meters
3. 1/5 km=1000/5=200 meters
4. 2/5 km=2000/5=400 meters
5. 3/4 km=3000/4=750 meters
6. 1/8 km=1000/8=125 meters
It's closed under addition. You can take any two natural numbers you want, add them up and you'll get some other natural number (eg: 3 and 5 ---> 3+5 = 8)
it's not closed under subtraction. Sure 5-3 = 2 is a natural number but 3-5 = -2 is not a natural number
so that leads us to the answer being choice B
