Sorry that I don't have the answer. Hope this helps!
Remember that any whole number can be written with a decimal point. For example: 2,890,000,000 = 2,890,000,000.0
Now, move the decimal place until you have a number between 1 and 10. If you keep moving the decimal point to the left in 2,890,000,000 you will get 2.89.
Next, count how many places you moved the decimal point. You had to move it 9 places to the left to change 2,890,000,000 to 2.89. You can show that you moved it 9 places to the left by noting that the number should be multiplied by 109
