А) (48 +k) • 8 = 400; г) 54 : (х - 16) + 22 = 31;
б) 3 • (х + 1) - 12 = 24;
д) (45 - x) • 2 - 7 = 45;
в) 45 :(17-x) + 9 = 24;
е) 812 : (х - 6) = 4;
ж) (x - 56): 12 = 37

Пошаговое объяснение:

а) (48 +k) • 8 = 400;

48+k = 400:8

48+k=50

k = 50-48

k=2

г) 54 : (х - 16) + 22 = 31;

54:(x - 16)=31-22

54:(x - 16) = 9

x - 16 = 54:9

x - 16 = 6

x = 6+16

x = 22

б) 3 • (х + 1) - 12 = 24;

3x + 3 = 24+12

3x + 3 = 36

3x = 36 - 3

3x = 33

x = 33:3

x = 11

д) (45 - x) • 2 - 7 = 45;

(45 - x)*2 = 45+7

(45 - x)*2 = 52

45 - x = 52:2

45 - x = 26

x = 45 - 26

x = 19

в) 45 :(17-x) + 9 = 24;

45:(17-x)=24-9

45:(17-x)=15

17-x = 45:15

17-x = 3

x = 17 - 3

x = 14

е) 812 : (х - 6) = 4;

x - 6 = 812 : 4

x - 6 = 203

x = 203+6

x = 209

ж) (x - 56): 12 = 37

x - 56 = 37*12

x - 56 = 444

x = 444+56

x = 500