Sophie's favorite number is a two-digit number. If she reverses the digits, the result is 36 less than her favorite number. Also, one digit is 3 more than double the other digit. What is Sophie's favorite number?

Sophie's favorite number is 85.

[10a + b] - [10b + a] ==36,

a=2b + 3, solve for a, b

Use substitution to get:

a =5 and b=1

And Sophie's favorite numbers is: 51