Have you spoken to X about this? (First response is to push back on the request and suggest an alternate person to speak to).
If you were able to do X first would that help? (Make a suggestion in the form of a question and hand control back to the other person).
Can I schedule it in for X, I’ve just no availability right now. (Give them an option to do it at another time but also let them know you have your own priorities).
Have you considered doing X first? (Again, it can sometimes be the best approach to lead with a suggestion of an action.)
Could you run that by X and come back to me? (Direct them to someone better qualified, who can assess the request and maybe answer the need before they have to deal with you).
I hear you and would love to help, I just have no resources right now? (Let them know you understand their predicament and need but also softly but assertively indicate that you have no capacity to deal with their needs right now.)
A leader’s job is not always to jump in and fix the problem but to advise, suggest, guide, coach and empower others to learn how to do it for themselves. It’s hard to lead when you’re down in the weeds. If you educate your team to ask these questions of themselves before they come to you, it reduces the day-to-day activity you get dragged into and empowers them.