0,5-1 5/16:(2,25+(0,75-2 5/8:7))=

1)2 5/8:7=21/8*1/7=3/8=0,375
2)0,75-0,375=0,375
3)2,25+0,375=2,625
       2,625=2 625/1000 = 2 5/8  (сокращаем на 125)
4)1 5/16: 2 5/8=21/16:21/8=21/16*8/21=1/2=0,5
5)0,5-0,5=0