Answer:
7.83 * 10^-7
Explanation:
In order for the expression to be valid, you have to be working with a whole number, so you take 0.000000783 and make it 7.83
Count the amount of placement you just removed and take 10 and put it to the power of the number of placement you removed (10^7).
In this case you are making the number smaller instead of bigger so the exponent is negative.
If you were making 7.83 into, for example, 70,830,000 then the scientific notation would be 7.83 * 10^7. The exponent would be positive.
Hope this isn't confusing and you can understand it. Have a good day! :)