I am a three digit number. the sum of my digits are 26. my last two digits are the same

There is one possible answer and that is 899. 9 and 9 are the same numbers (duh!) and 8 + 9 + 9 is 26.

Xyz

x+y+z=26

y=z

subsitute y for z

x+z+z=26

x+2z=26

we know that the sum is 26 so therefor none of the numbers can be more than 9

try and subsitute 9 for z

x+9+9=26

x+18=26

subtract 18

x=8

try 8 for z

x+8+8=26

x+16=26

subtract 16

x=10

impossible since 10>9

therefor the number is 899