What is the value of the expression 8.3 × 104 − 2.5 × 103 − 1.9 × 104 written in scientific notation?

Remark work with the two numbers that are 10^4 first. Then add in the one that goes to 10^3

Method one
You could change these all to integers and then take it back to scientific notation.

 83 000
-19 000
  64 000
-   2 500
  61 500 <<<<<< answer

Method two
Keep the scientific notation.
 8.3 * 10^4
-1.9 * 10^4
 6.4 * 10^4
-  .25*10^4  Note the powers of ten must be the same.
  6.15*10^4 <<<<<<<< answer

Either method works. 

You could use your calculator to get the right answer. I'm not sure all calculators retain the scientific notation. Test yours to see what it does. Enter 8.3*10y^x 4 *1 = 

Your calculator might have x^y or ^ to record powers. You may also have EE and one of your keys.

See if your calculator returns 8.3*10^4 or if it returns 83000