The earths diameter through the equator is about 8000 miles. what is the earths estimated diameter written as a whole number multiplied by a power of ten

So,

To write 8000 miles in scientific notation, first find a natural number between 1 and 10.
8

Now, figure out how many decimal places we have to move to the left.
8000.0 --> 8.0000
Three

Now, write the number 8 multiplied by 10 to the third power.