So first I know that 9.8 is closest to a tidy number, so I added 0.2 to get to 10. Since I done that I have to do that to the other number.
So 25.6+0.2=25.8. This leads us to a new question to answer. 25.8-10 and that equals 15.8. As you can see this is a really easy strategy to do.