(3x 10^-3)(2x10^9) express in scientific notation

; you need to multiply 3 and 2, which gives you 6, and then add the exponents of the tens. In this case,  equals 6, so the exponent will be six, but the ten won't change.

If you have a scientific calculator, it's even easier. First press mode, which should probably be a button near the top left, depending on which type of calculator you have. Change the mode from norm (normal) to sci (scientific). Then if you just write in the numbers (using parentheses), you should get them in scientific notation. Just make sure you change the mode back to normal or all numbers will come out in scientific notation.

Hope this helped :)