a) $57 + (7 - 32) = 319 - (x + 319)$
$⇒57 - 25 = 319 - x - 319$
$⇒x=319-319+25-57$
$⇒x = -32$
b) $(76 - x) - (67 - x) = 9 - (-2 + x)$
$⇒76 - x - 67 + x = 9 + 2 - x$
$⇒-x + x + x = 9 + 2 - 76 + 67$
$⇒x = 2$
c) $x - {34 - [26 + (-66 - x)]} = 27 - {43 + [25 - (20 - x)]}$
$⇒x - [34 - (26 - 66 - x)] = 27 - [43 + (25 - 20 + x)]$
$⇒x - (34 + 40 + x) = 27 - (43 + 5 + x)$
$⇒x - 74 - x = 27 - 48 -x$
$⇒x - x + x = 27 - 48 + 74$
$⇒ x = 53$