1. Move the decimal point to the right until you have a number between 1 and 10. In this case, you'd move it seven places to the right: 1.25

2. Count the number of places you moved the decimal. Since you moved it seven places to the right, the exponent will be -7.

3. Write the number in the form a x 10^b, where 'a' is the number between 1 and 10 and 'b' is the exponent: 1.25 x 10^-7