this is happening with me that i have solved question before 10-15 days before but now I can't recall that question

You don't need to worry about such a thing, this is very common and happens with everybody. No one can recall or cram all the questions they do.

You just have to make sure you understand the concept behind questions and as you practice more and more questions of the same topic, you can easily solve any new question that comes in the paper.

And if you are referring to the factual subjects like history or political science, I will advise you to maintain handwritten notes of each topic and revise them thoroughly before any examination.

Hope this helps !