Doug is twice Anne's age. Doug is 34 years old. How old is Anne?
Represent the unknowns: d for Doug, a for Anne.
Then d=34 years.
Doug is twice Anne's age, so d=2a. But d=34 yrs, so 34 yrs = 2a.
Solve this for a: a = 34 yrs / 2 = 17 yrs
Doug is 34, Anne is 17.