8 7/10 - ( 7 4/5 - a ) при а=6 1/2;

8 7/10 - ( 7 4/5 - 6 1/2 ) = 7 2/51) 7 4/5 - 6 1/2 = 1 8-5/10 = 1 3/102) 8 7/10 - 1 3/10 = 7 7-3/10 = 7 4/10 = 7 2/5