Need Help with solving Delay Differential Equations by Variation of Parameters Method

Hi friends,
I am new to this forum. I stumbled upon this forum while searching for the solution of my Maths assignment.

My Assignment reads:
"Solve by method of variation of parameters a 3rd order delay differential equation".

After days of search online i still have not been able to find its solution. The closest i got is solving 1st order DDEs by variation of parameters. (thru google books)

Please can someone point me in the right direction?? I would really appreaciate any help.

Thanks for reading.

Where is the equation? or do you want help with something else?

PS. If you're looking for the VP method for higher order DE's, Boyce-DiPrima is a good source.