Standard form is always a number between 1 and 10 (but never exactly 10) multiplied by 10 to the power of something. Just divide the 25 by 10, so it can be used in standard form, and increase the power by 1. Hope this helped! :^)
Explanation: In order for 25 • 10^6 to be written in standard form, the ‘25’ needs to be less than 10. To do that we will move the decimal one place to the left so that 25 is now 2.5; it is now a number less than 10. It should now look like 2.5 • 10^6. It is now in standard form.
9 × 9 would be the answer or just 9. Since 9 × 9 = 81. So, I believe you could put 9 if there is only one x spot but if there is 2 you can put 9 × 9. Hope this helps! c: