To solve this we need to move the decimal to get greater then 1 and less then 10.
So to do this move the decimal over (the right)
Now we have 0.07 = 7x10^-2
We had to move the decimal 2 places over to get 7 and since we moved it to the right, its going to be a negative.
Your answer is
0.07 = 7x10^-2