Найдите значение выражения. 8-4.2: (2целых5/14-1целая4/21)=

8 - 4.2 : (2 5/14 - 1 4/21) = 8 - (4 1/5) : (33/(2*7) - 25/(3*7)) = 8 - 21/5 : (99/42 - 50/42) = 8 - 21/5 : 49/42 = 8 - 21/5 : 7/6 = 8 - 21/5 * 6/7 = 8 - 18/5 = 8 - 3 3/5 = 5 - 3/5 = 4 2/5;