What’s my number? I am a three-digit number. My units digit is twice my hundreds digit. My tens digit is the sum of the other two. And I am the largest of such three-digit numbers.

well if the units digit is twice the hundreds digit, then the options are:

1x2
2x4
3x6
4x8

with x being any digit 0-9.

Since the tens digit is the sum of the other 2 digits, then that eliminates 4x8, because the sum is bigger than 9.
So that leaves:
132
264
396

That last part says it is the largest of those numbers, which means the answer is:

396