Aconstant force is applied to an object, causing the object to accelerate at 10 m/s^2. what will the acceleration be if: a) the force is halved? b) the object's mass is halved? c) the force and the object's mass are both halved?

What you need to know is that the force is

F=ma

The force is the product of mass and acceleration

this means that the acceleration is

a=F/m

a) The force is halved?
this means that f will be now:

a=

So the accelaration will also he halved (it's the original acceleratation divided by 2)

 b) The object's mass is halved?
a==a=

which is the original acceleration times two!! so it will double

c) The force and the object's mass are both halved?
now we have

a==a==a=

so they will cancel each other out and the acceleration will stay the same!