because it will be 9-16 which will equal to -7 due to the fact that 9 is smaller than 16 and when you subtract a small number from a big number you get a negative number.

My explanation might be a little confusing but let me know if you need help. I might be able to explain it better. Or try using a calculator when you plug in 9-16 it will give you -7. why? because you are plugging 9 (small number)first and than the 16 (large number).