David reads 80 pages every day.
Karen reads 25% more pages every day than David reads.
So, Karen reads [tex]\frac{25}{100}*80= 20[/tex] more pages. She reads a total of 80 + 20 =100 pages.
Rick reads 35% fewer pages per day than Karen. So, Rick reads [tex]\frac{35}{100}*100=35[/tex] less pages than Karen. He reads 100 - 35 =65 pages
So, in total the tree friends read = 80+100+65=245 pages.
So, equation becomes [tex]245d=10000[/tex]