Question 1066632
So currently we have 8 yellow and 6 blue marbles. We need to add an amount to yellow marbles to make it so that the ratio is 2:1.

We can set it up like this.  Let x be the amount that we add to the yellow marbles.

Then  (8+x)/6 = 2/1

So 8+x = 12 by cross multiplication.

x = 4

So we can add 4 yellow marbles to get a ratio of 2:1.