Marcy loves to do puzzles. Last week, she spent 2 hours putting together a puzzle with 300 pieces. This week, she wants to put together a puzzle with 450 pieces.
If she keeps the same pace, how many hours should it take Marcy to put the puzzle together this week?
If Marcy spent 2 hours putting the 300 piece puzzle together, then she spent 2/300=1/150 of an hour per piece.
So it would take her 450*(1/150)= <<450*(1/150)=3>>3 hours to put together a 450 piece puzzle. Answer: \boxed{3}.