Marcus and his twin sister Marcie decide to save $25 each week to buy a video console. How long will it take for them to save $675?(
Since both Marcus and Marcie are saving $25 each week, their combined saving per week would be $25 + $25 = $<<25+25=50>>50.
To calculate the number of weeks it will take them to save a total of $675, we divide the total amount they want to save by their combined saving per week: $675 / $50 = 13.5 weeks.
Since they cannot save for a fraction of a week, they will need to save for 14 weeks before they can afford the video console. Answer: \boxed{14}.