Let "x" represent the age of Brian.
Andrew is elder than Brian by 2 years, we can symbolize his age as "x+2"
Frank is twice as old as Andrew, we can symbolize his age as "2(x+2)"
Sarah has half the age of Brian's, we can symbolize her age as "x/2"
Frank ans Sarah's ages differ by 40 years, we can symbolize this as:
Solve the term is parenthesis
x=24 years
Andrew's age is
Andrew is 26 years old