Present ages of sita and ram are 12 yrs and 24 yrs respectively.
let x years ago, ram's age be thrice as sita's age.
x years ago
ram's age = (24-x)
sita's age = (12-x)
now, ram's age = 3(sita's age)
hence, 6 yrs ago, ram's age was thrice as sita's age