Вправи: 569

569. Розв’яжіть рівняння:

1) 28 + ( 45 + x) = 100; 28 + 45 + x = 100; 73 + x = 100;

x = 100 – 73; x = 27

2) (y – 25) + 18 = 40; y – 25 = 40 – 18; y – 25 = 22; y = 22 + 25;

y = 47

3) (70 – x) – 35 = 12; 70 – x = 12 + 35; 70 – x = 47; x = 70 – 47;

x = 23

4) 60 – (y + 34) = 5; 60 – 5 = y + 34; 55 = y + 34; 55 – 34 = y;

21 = y; y = 21

5) 52 – (19 + x) = 17; 19 + x = 52 – 17; x + 19 = 35; x = 35 – 19; x = 16

6) 9у – 18 = 72; 9у = 72 + 18; 9у = 90; у = 90 : 9; у = 10

7) 20 + 5x = 100; 5x = 100 – 20; 5x = 80; x = 80 : 5; x = 16;

8) 90 – y • 12 = 78; y • 12 = 90 – 78; y • 12 = 12; y = 12 : 12;

y = 1

9) 10x – 44 = 56; 10x = 56 + 44; 10x = 100 : 10; x = 10

10) 84 – 7y = 28; 7y = 84 – 28; 7y = 56; y = 56 : 7; y = 8

11) 121 : (x – 45) = 11; x – 45 = 121 : 11; x – 45 = 11;

x = 11 + 45; x = 56

12) 77 : (y + 10) = 7; y + 10 = 77 : 7; y + 10 = 11; y = 11 – 10;

y = 1

13) (x – 12) : 10 = 4; x – 12 = 4 • 10; x – 12 = 40; x = 40 + 12;

x = 52

14) 55 – y • 10 = 15; y • 10 = 55 – 15; y • 10 = 40; y = 40 : 10;

y = 4

15) x : 12 + 48 = 91; x : 12 = 91 – 48; x : 12 = 43; x = 43 • 12;

x = 516

16) 5у + 4у = 99; 9у = 99; у = 99 : 9; у = 11

17) 54x – 27x = 81; 27x = 81; x = 81 : 27; x = 3

18) 36y – 16y + 5y = 0; 25y = 0; y = 0; y = 0 : 25; y = 0

19) 14x + x – 9x + 2 = 56; 6x + 2 = 56; 6x = 56 – 2; 6x = 54;

x = 54 : 6; x = 9

20) 20y – 14y + 7y – 13 = 13; 13y – 13 = 13; 13y = 13 + 13;

13y = 26; y = 26 : 13; y = 2.