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Пошаговое объяснение:

1)

7x – 4 = x – 16

7x - x = -16 + 4

6x = -12

x = -12 : 6

x = -2

2)

13 – 5x = 8 – 2x

5x - 2x = 13 - 8

3x = 5

x = 5 : 3

x = 1 2/3

3)

13p – 11 = 8p + 5

13p - 8p = 5 + 11

5p = 16

p = 16 : 5

p = 3,2

4)

71x – 13 = 10 – 29x

71x + 29x = 10 + 13

100x = 23

x = 23 : 100

x = 0,23

5)

31(1 – 3t) + t = 4(t – 14)

31 - 93t + t = 4t - 56

31 - 92t = 4t - 56

4t + 92t = 31 + 56

96t = 87

t = 87 : 96

t = 87/96

6)

2 = (3x – 5) – (7 – 4x)

3x - 5 - 7 + 4x = 2

7x - 12 = 2

7x = 2 + 12

7x = 14

x = 14 : 7

x = 2

Вариант II

1)

8x – 5 = x – 40

8x - x = -40 + 5

7x = -35

x = -35 : 7

x = -5

2)

7t + 24 = t – 3

7t - t = -3 - 24

6t = -27

t = -27 : 6

t = -4,5

3)

3p – 5 = 6 – 7p

3p + 7p = 6 + 5

10p = 11

p = 11 : 10

p = 1,1

4)

831x – 71 = 111x + 1

831x - 111p = 1 + 71

720x = 72

x = 72 : 720

x = 0,1

5)

2(x – 3) – 1 = 5(x +3) – 4

2x - 6 - 1 = 5x + 15 - 4

2x - 7 = 5x + 11

5x - 2x = -7 - 11

3x = -18

x = -18 : 3

x = -6

6)

12 = (7x – 9) – (11 – x)

7x - 9 - 11 + x = 12

8x - 20 = 12

8x = 12 + 20

8x = 32

x = 32 : 8

x = 4

Округлите числа:
1) 75=80; 34=30; 816=820; 42=40; 1859=1960; 6394=6390 — до десятков;
2) 612=600; 871=900; 1304=1300; 1950=2000 — до сотен;
3) 5402=5000; 2 783 430 456=278343000; 84 609=85000 - до тысяч;
4) 6 009 842=6010000; 15 624 035=15620000; 34 567=30000 - до десяти тысяч;
5) 77,57=78; 124,1=124; 16,027=16; 421,87=422; 3,94=4 — до целых;
6) 657,239=657,2; 0,512=0,5; 57,429=57,4; 99,98=100 - до десятых;
7) 0,07 612=0,08; 8,571=8,56; 13,042=13,04; 1,9507=1,95 - до сотых;
8) 8,32 715=8,327; 49,0562=49,056; 748,0998=748,1 - до тысячных.