Answer:
258.3
Explanation:
When you're multiplying a decimal with a factor of 10, you would move the decimal places to the right, which is dependant on how many zeros the number actually has.
100 has 2 zeros, yes?
100 x 2.583 is 258.3, as you would the decimal places 2 to the right, which results in the value being 258.3.
Hope this helped! :)