a) $$ (a - 15) - 16 = 18 $$
$$ a - 15 = 18 + 16 $$
$$ a - 15 = 34 $$
$$ a = 34 + 15 $$
$$ a = 49 $$
б) $$ (x - 41) - 21 = 8 $$
$$ x - 41 = 8 + 21 $$
$$ x - 41 = 29 $$
$$ x = 29 + 41 $$
$$ x = 70 $$
в) $$ (136 - x) - 16 = 52 $$
$$ 136 - x = 52 + 16 $$
$$ 136 - x = 68 $$
$$ x = 136 - 68 $$
$$ x = 68 $$
г) $$ (558 + x) - 52 = 746 $$
$$ 558 + x = 746 + 52 $$
$$ 558 + x = 798 $$
$$ x = 798 - 558 $$
$$ x = 240 $$
Заменим первые цифры ответов на буквы. Получим слово ЧАЙКА.