№154.
1) -n=-7.4
2)-n=16.1
#155
1)x=-43
2)x=82
#156
1)x=-20
2)x=36
3)x=-18
7,4(а+b)+0,5(a-b)=7,4a+7,4b+0,5a-0,5b=(7,4a+0,5a)+(7,4b-0,5b)=7;9a+6;9b
1) = (6 + 3) + (4/9 + 5/9) = 9+ 9/9 = 9 + 1 = 10
2) = (10 + 5) + (11/19 + 14/19) = 15 + 25/19 = 16 6/19
3) = (2 + 2) + (3/13 + 11/13) = 4 + 14/13 = 5 1/13
4) = (1 + 3) + (5/8 + 7/8) = 4 12/8 = 5 4/8 = 5 1/2
5) = 1 - 3/11 = 11/11 - 3/11 = 8/11
6) = 40/40 - 13/40 = 27/40
7) = 3 7/7 - 1 4/7 = 2 3/7
8) = (1 + 9) - 9 3/10 = 1 - 3/10 = 10/10 - 3/10 = 7/10
9) = (3 + 2) + 2/7 - 2 5/7 = 3 2/7 - 5 /7= 23/7 - 5/7 = 18/7 = 2 4/7
10)= 13 26/20 - 8 12/20 = 5 14/20 = 5 7/10
11)= 7 17/14 - 5 9/14 = 2 8/14 = 2 4/7
12) = 6 31/21 - 4 16/21 = 2 15/21 = 2 5/7
13)= 8
14) = (19 22/22) - (12 30/23- 9 15/23) = 20 - 3 15/23 = 16 8/23
Так как 8 дм - это 1/5 часть ленты,
то вся лента: 8 : 1/5 = 8 * 5 = 40 (дм)
40 дм = 4 м
Ответ: длина всей ленты 4 м.