A mobile number consists of ten digits. First four digits are 9,9,7 and 9. Make the smallest mobile number by using only one digit twice from the digits 8,3,5,0,6?

Hint: So, in the question we have to frame the smallest mobile number possible by using only one digit twice, so choose the smallest digit number in the given numbers and use it twice one after another, now when you use the smallest digit number twice after the first four digits then use the remaining numbers in the ascending order then the number automatically forms the smallest mobile number possible.

Complete step-by-step answer:
So, the mobile number is $9\,9\,7\,9\,\_\,\_\,\_\,\_\,\_\,\_$
And to complete the mobile number we have to use the digits $8,3,5,0,6$ and one of the given numbers twice
So, choose the numbers in the ascending order
(Ascending order: arranging the numbers in the form of smaller values to lower values)
(Descending order: arranging the numbers in the form of larger values to smaller values)
Ascending order is $0\,0\,3\,5\,6\,8$ using the smaller number twice.
So, from the above analysis the smallest mobile number is $9\,9\,7\,9\,0\,0\,3\,5\,6\,8$.

Note: When the question says you about a smaller number, arrange the numbers in the ascending order and when the question says you about the largest number possible, arrange the numbers in the descending order.