Assuming force is constant, how does the mass of an object affect its acceleration?

Well a simple way to investigate this is to use the formula

Force = Mass x Acceleration

so if force is constant say 10 units

10 = mass x acceleration

if the mass is 5 units the acceleration is 2 units

if the mass is 1 unit the acceleration is 10 units

if the mass is 1/2 units the acceleration is 20 units

so hopefully you can see a pattern occurring that you can generalise for your answer