Answer
(a) $2°~30'$
(b) $-3°~34'~48''$
Work Step by Step
$1'=60''$
$1°=60'$
$1°=60'\times\frac{60''}{1'}=3600''$
(a) $2.5°=2°+0.5°·\frac{60'}{1°}=2°~30'$
(b) $-3.58°=-(3°+0.58°·\frac{60'}{1°})=-(3°~34.8')=-[3°~(34'+0.8'·\frac{60''}{1'})]=-3°~34'~48''$