Add:
$3$ days $21$ hours and $5$ days $18$ hours

Add:

$59$ hours $45$ minutes and $68$ hours $20$ minutes

Subtract :

$9$ days $19$ hours from $11$ days $48$ hours

Subtract :

$8$ hours $46$ minutes from $16$ hours $21$ minutes.

Subtract:

$39$ minutes $39$ seconds from $80$ minutes $14$ seconds.