How should the number 1.230 x 103 be properly expressed as a decimal?

1,230
Usage of 10^x form is called scientific form and it helps much in science where the calculation unit can vary from very big into very small.
In this case, you are given the number 1.230 x 10^3  and asked to express it in decimal form. Then you just simply need to multiply the number with the 10^3. The calculation  would be: 1.230 x 10^3= 1.230 x 1000= 1230