Aparticular interaction force does work wint inside a system. the potential energy of the interaction is u. which equation relates u and wint

ΔU = -Wint

Consdier the work of of interaction is W =m*g*h - equation -1

and the Potential energy U.

Final Potential energy Uf =0 , And the Initial Potential Energy Ui =m*g*h

Now we will write the equation for a Change in Potential energy ΔU,

ΔU = Uf - Ui

= 0-m*g*h

  ΔU = -m*g*h --Equation 2

Now compare the both equation

Wint = -ΔU

we can rewrite the above equation

ΔU = -W.

So our Answer is ΔU = -W. .