I believe the answer is 6 white marbles. how i figured that out was i made an equation. i took the variable Y (for the yellow marbles) times 2 minus 6 equals 18. you then add 6 to the other side of the equal sign to cancel out the 6. you then have y(2)=24. you divide y and 24 by 2. you get 12 yellow marbles. next step is to take 18 - 12. you are left with 6 white marbles. hope this helps!
With 10 to the power to a negative number, it's easier.
Here's a trick: The negative number is the places to the right of the decimal. The last number is a 1, while the rest are 0s.
From this, we get:
The answer is 3 because the length of the box is 10, the width is 5, and the height is 3.