За полчаса он прошел 6 км, значит за час пройдет 6 + 6 = 12 км
( 2/7 + 3 1/4) - ( 11/14 + 13/28 )= 2.28571428571
19/9*3/7+21/4*8+
+(82/15*1/41-5/2*4/15)=
19/21+42+(2/15-2/3)=
=42 19/21-8/15=
=42 95/105-56/105=
=42 39/105=42 13/35
45/7*7/9*10/3/1*4/21*4/21=
=50/3*441/16=25*147/8=
=3675/8=459 3/8