The answer for her (Monica) dad's swimsuit is $65. Since the amount of Monica's swimsuit is $35, and it was mentioned that her mom's is twice as much of her, then her mom's swimsuit will cost $70 ($35*2=$70). If we will add the amount of their swimsuit, that will be $105. As per mentioned, they spend $170 for the swimsuit. So the equation will be $170 (total amount spent on swimsuit) - $105 (amount for Monica and her mom's swimsuit) = $65 (amount of her dad's swimsuit).
