#### Answer

a)
a = 8/2 m/s^2
a = 4 m/s^2
b)
a = 8x2 = 16 m/s^2
c)
a =8 m/s^2

#### Work Step by Step

a)
We know that
F = m x a.
If m is constant, F is directly proportional to acceleration.
So
if force is halved acceleration becomes half.
So
a = 8/2 m/s^2
a = 4 m/s^2
b)
We know that
F = ma.
If F is constant mass x acceleration will be constant.
If mass is halved, keeping force constant,
acceleration becomes double.
So
a = 8x2 = 16 m/s^2.
c)
We know that
F = ma
a = F/m.
So if both F and m are doubled, the acceleration will be the same.
a =8 m/s^2