Jimmy's sister is twice as old as he is. His big brother is 5 years older than he is. The sum of their three ages is 29. How old is Jimmy's brother?

11 years old

Step-by-step explanation:

Let Jimmy's age be represented as x. His big brother's age is x+5 and his sister's age is 2x. Adding these gives us 4x+5=29. Solving for x gives us 6. His brother's age is 6+5=11.