Answer: Marta worked 13 hours overtime.
Explanation:
1): You do 25 x 36 to get the amount of money she can make before she starts to make double.
36 x 25 = 900
2): Minus $900 from $1550
$1550 - $900 = $650
3): Divide $650 by $50
$650 / $50 = 13 hours worked overtime