Answer: The only two numbers that allow us to make the fraction reducible are 4333 and 3333. (So the digit can be 4 or 3)
Step-by-step explanation:
77 can be written using prime numbers as:
7*11 = 77
So the only way in which we can make the fraction reducible is if the number
...333 is a multiple of 7 or 11. (so we can write it as 7*something or 11*something)
333 is not a multiple of 7 nor 11.
1333 is not a multiple of 7 nor 11
2333 is not a multiple of 7 nor 11
3333 is a multiple of 11, (11*303 = 3333) then this number can make the fraction reducible.
then 77/3333 = 7/303
4333 is a multiple of 7, (7*619 = 4333) then this number can make the fraction reducible
then 77/4333 = 11/619
5333 is not a multiple of 7 nor 11
6333 is not a multiple of 7 nor 11
7333 = is not a multiple of 7 nor 11
8333 = is not a multiple of 7 nor 11
9333 = is not a multiple of 7 nor 11
The only two numbers that allow us to make the fraction reducible are 4333 and 3333.