1,4*(28+x)+2,2=1,7*(28-x)
39,2+1,4x+2,2=47,6-1,7x
1,4x+41,4=47,6-1,7x
1,4x+1,7x=47,6-41,4
3,1x=6,2
x=6,2:3,1
x=2км/ч скорость течения реки
1. 1) 3 1/4 +2 2/3=13/4 + 8/3= 71/12 = 5 11/12
2) 11/18 - 5/9 = 1/18
3) 5/7 х 21/25 = 3/5
4) 2 1/13 : 1 19/26 =27/13 : 45/26= 27/13 х 26/45 = 6/5 =1 1/5
6. 7/25= 14/50 14/50 < 15/50
3/10 = 15/50 7/25 < 3/10
8. 6 3/7 : 9/14 - 1 1/19 х ( 3,2 - 2 1/4) =
1) 6 3/7 : 9/14 = 45/7 х 14/9 =10
2) 3,2 - 2 1/4 = 32/10 - 9/4 = 38/40 = 19/20
3) 1 1/19 х 19/20 = 20/19 х 19/20 = 1
4) 10-1 =9
54 = 2 x 3 x 3 x 3
90 = 2 x 3 x 3 x 5
НОК = 2 x 3 x 3 x 5 x 5 = 270