Narenn wrote:

If X is a three-digit integer, what is the value of its tens digit?

(1) The tens digit of X+8 is 5.

(2) The units digit of X+9 is 7.

let the number be 100a+10b+c

st.1 ) if c=1 or 0; then tens digit will be 5 and if C=2 (or greater than 2)then tens digit will be 4

as different values of tens digit are possible for different values of c hence insufficient

st.2) C+9 will yield unit digit of 7, when C=8. Since no information is provided about tens digit hence insufficient

combining 1 and 2 we know that, if C is greater than or equal to 2 then tens digit is 4. hence sufficient.