Answer
$19^{\circ}59'24''.$
Work Step by Step
We know that $1^o = 60’$
$1’=60"$
Use a calculator and the conversion factors above to obtain:
$19.99^{\circ}\\=19^{\circ}+0.99\cdot60'\\=19^{\circ}+59.4'\\=19^{\circ}+59'+0.4\cdot60''\\=19^{\circ}+59'+24''.$