(x + 15) - 8 = 17
x + 7 = 17
x = 17 - 7
х= 10
проверка: (10 + 15) - 8 = 25 - 8 = 17
(24 + x) - 21 = 10
x + 3 = 10
x = 10 - 3
х= 7
проверка: (24 + 7) - 21 = 31 - 21 = 10
55 - (х - 15) = 30
х - 15 = 55 - 30
х = 25 + 15
х= 40
проверка: 55 - (40 - 15) - 55 - 25 = 30
(x + 15) - 8 = 17
x + 7 = 17
x = 17 - 7
х= 10
проверка: (10 + 15) - 8 = 25 - 8 = 17
(24 + x) - 21 = 10
x + 3 = 10
x = 10 - 3
х= 7
проверка: (24 + 7) - 21 = 31 - 21 = 10
55 - (х - 15) = 30
х - 15 = 55 - 30
х = 25 + 15
х= 40
проверка: 55 - (40 - 15) - 55 - 25 = 30