I agree with Insaf Ali Shar, No doubt, the best way to prepare ability portion is to teach others. I am myself a teacher and have been teaching to various aspirants. Teaching and discussions helped me a lot in this regard. Videos are recommended to comprehend the basic concepts. Otherwise, Mathematics is by practice only. Try to solve as much questions as you can, and, teaching others is a good way of practice.

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جب خشت بنے تب کام چلے