https://preparationpoint.info/mathematics-mcqs/basic-maths-mcqs/a-and-b-can-finish-a-work-30-days-if-they-work-together-they-worked-together-for-20-days-and-then-b-left-a-finished-the-remaining-work-in-another-20-days-in-how-many-days-a-alone-can-finish-the-wor-2/