Answer
(a) $-345°~7'~12''$
(b) $27'$
Work Step by Step
$1'=60''$
$1°=60'$
$1°=60'\times\frac{60''}{1'}=3600''$
(a) $-345.12°=-(345°+0.12°·\frac{60'}{1°})=-(345°~7.2')=-[345°~(7'+0.2'·\frac{60''}{1'})]=-345°~7'~12''$
(b) $0.45°=0.45°·\frac{60'}{1°}=27'$