Solve it with steps pls if possible

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?

When you have 25 numbers, and jake picks 3 random numbers and puts them back, what is the chance bob has of picking those 3 numbers when he picks 6 random numbers (without putting them back)? explain.

What is the measure of sty in oo below? 130 310 230 50