Question

what is complementary angle of (10x-88)?

Answer 1

If $x$° is any angle, then its complementary angle is always $(90-x)$°. 
Here, $(10x-88)$° is the given angle. 
So, its complementary angle is 
$[90-(10x-88)]$°
$= (90-10x+88)$°
$= (90+88-10x)$°
$= (-10x+178)$°

Hope this may help you.