a - 986 = 3974
a = 3974 + 986
a = 4960
y + 1138 = 4000
y = 4000 - 1138
y = 2862
x - 2765 = 7081
x = 7081 + 2765
x = 9846
k + 40521 = 50521
k = 50521 - 40521
k = 10000
Ответ: a = 4960, y = 2862, x = 9846, k = 10000