Here's how to get there:

1. Move the decimal point to the left until you have a number between 1 and 10. In this case, we move it three places to the left, resulting in 7.8.

2. Count the number of places you moved the decimal. Since we moved it three places, the exponent of 10 is 3.

3. Combine the results to get 7.8 x 10³.