When someone asks for your help, give them a chance to fix it first.
It will make the experience more pleasant for they don't realise you are teaching them something.
Stepping in means you don’t trust they can handle the situation – and what you think of them matters, it will influence their confidence and their appetite for risk taking. It may take them longer than you would like for them to find the solution, but let them show you they are competent for the job.
Give them a chance to impress you and show you they are better than you thought.
And give yourself the chance to be surprised by the wonderfully creative ideas they come up with. There is nothing more motivating than to know your colleagues and managers trust you can do it.