1)550*3=1650(км)- пролетел 1-ый
2) 3540 - 1650= 1890(км)- пролетел 2-ой
3) 1890/3= 630 (км/ч) - скорость 2-ого
1 8/11 + 2 2/19 * (1 4/5 - 2 3/4) = 19/11 + 40/19 * (9/5 - 11/4) =
= 19/11 + 40/19 * (9*4/5*4 - 11*5/4*5) = 19/11 + 40/19 * (36/20 - 55/20) =
= 19/11 + 40/19 * (- 19/20) = 19/11 - 40*19/19*20 = 19/11 - 40/20 = 19/11 - 2 =
19/11 - 22/11 = - 3/11
25t - 2,5 = 95,84
25t = 95,84 + 2,5
25t = 98,34
t= 3,9336
7 5/6 - 4 2/3 = 7 5/6-4 4/6=1 1/6