What’s the answer I don’t get it and hopefully you can help me. Like I need the answer now

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?

Manny bought 12 pounds of vegetables at the supermarket. 75% of the vegetables were on sale. how many pounds of vegetables were not on sale? 98 points : )

What is always true when two whole numbers are subtracted?