---

# Ограничения хранятся в виде списка словарей или кортежей: (a1, a2, знак, b)
system = [
    (2, 3, "<=", 18),
    (4, 1, ">=", 16),
    (1, 5, "=", 20)
]

x_counter = 3
for a1, a2, sign, b in system:
    if sign == "<=":
        print(f"{a1}*x1 + {a2}*x2 + x{x_counter} = {b}")
        x_counter += 1
    elif sign == ">=":
        print(f"{a1}*x1 + {a2}*x2 - x{x_counter} = {b}")
        x_counter += 1
    else:
        print(f"{a1}*x1 + {a2}*x2 = {b}")