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
ответ: s=40 кв.м.