Please explain step by step

Please explain step by step Exercise 1 (B) 1. the following questions. (i) In which order should the four different digits be arranged [o obtain the largest 4-digit number

Dear student,
 
Answer:Descending Order

Step-by-step explanation:
If we arrange the numbers in Descending Order then the largest number will get the highest place value and so we get the largest 4 digit number that can be formed from it.
Putting the largest available digit in the highest value place, and moving from left to right, we get 9876.

Hope, this clears your doubt.
Regards