We apply the gravity calculation expressed in the formula: g=GM/r2 
where G is the gravitational constant, m is the mass and r is the radius
r=√GM/g
(1)       Radius = √6.674e-11*5.972e24/8             = 7058 kms    Earth radius or surface of earth from center of earth= 6400 kmsSo r= 658 kms from surface of earth.
Gravity 8m/s2 will be at 658 kms from surface of earth.
(2) half gravity= 9.8/2= 4.9 m/s2     Radius=√6.674e-11*5.972e24/4.9                 = 9019 kms        Half Gravity will exist at 9019-6400= 2619 kms from surface of earth.
        
             
        
        
        
I got B,when you subtract 3/5 from NEGATIVE 2/3 it creates a negative 19 over a positive 15.
        
             
        
        
        
C is the awnser because c is single replacement
        
             
        
        
        
Answer:
new atmospheric pressure is 0.9838 ×  Pa
  Pa
Explanation:
given data 
height = 21.6 mm = 0.0216 m
Normal atmospheric pressure = 1.013 ✕ 10^5 Pa
density of mercury = 13.6 g/cm³
to find out
atmospheric pressure 
solution
we find first height of mercury when normal pressure that is 
pressure p = ρ×g×h 
put here value
 1.013 ×  = 13.6 × 10³ × 9.81 × h
  = 13.6 × 10³ × 9.81 × h 
h =  0.759 m
so change in height Δh = 0.759 - 0.0216
new height H = 0.7374 m
so new pressure = ρ×g×H
put here value
new pressure = 13.6 × 10³ × 9.81 × 0.7374
atmospheric pressure = 98380.9584
so new atmospheric pressure is 0.9838 ×  Pa
  Pa
 
        
             
        
        
        
Answer:
Planting of trees on sloped surfaces is a method of conservation that utilizes the roots of plants. Planting trees on such areas would prevent hazards and maintain the soil formation future since the roots would hold the soil together preventing or minimizing any soil erosion.