Please help to solve the problem using model


In a bag, there are red, yellow and blue marbles. There were twice as many red marbles as yellow marbles and twice as many yellow marbles as blue marbles at first. After removing 15 blue marbles and some yellow marbles from the bag, the number of red marbles became thrice that of the yellow marbles but the number of yellow marbles was still twice that of the blue marbles. What was the total number of marbles in the bag at first?[/size]

Please help to solve this probe.


Ali has 3 times more than Sam. After Ali lost 18 marbles and Sam bought 12 marbles, they have equal number of marbles. How many marbles did have at first?