98 is the answer.
98
679 is the product of the largest single-digit prime number and the largest two-digit prime number.
There can only be one largest two-digit prime number.
99
73 is the largest two-digit number that is prime and has prime numbers for both of its digits.
25
How about 89
269
50 - 25 = 25
99*99=9801
Subtract 25 from 50.
86
They are: 83, 89 and 97