So let's list our marbles:
B = 50%
G = 30%
R = 6
Out of 100%, if B is 50% and G is 30%, then that must mean R is 20%. Now that we know that 6 is 20% out of 100%, we can find out the total of marbles we have.
If 6 is 20%, then we multiply it by 5 to find out the total marbles.
So let's find out the number of blue and green marbles. For blue, 50% of 30 is 15 marbles. For green, 30% of 30 is 9 marbles.
The question asked to increase the blue marbles by 40%. So 40% of 15 is 6. Then we add this 6 to our blue marbles.
40% of 15 =
Let's relist our marbles:
B = 21
G = 9
R = 6
Now, all that's left is to add them all to get our total marbles.