Answer
$a)36^0$
$b)126^0$
Work Step by Step
If two angles are Complement then sum of these angles is $90^0$
If two angles are Supplement then sum of these angles is $180^0$
$a)\alpha+54^0=90^0\Rightarrow \alpha =90^{0}-54^{0}=36^{0};$
$b)\theta+54^0=180^0\Rightarrow \theta=180^{0}-54^{0}=126^{0}$