SOLUTION: Sana is senior to Mona by 18 years.After 6 years Sana will be twice as old as Mona.Find Mona,s prasent age

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Question 1062044: Sana is senior to Mona by 18 years.After 6 years Sana will be twice as old as Mona.Find Mona,s prasent age
Answer by math_helper(2461) About Me  (Show Source):
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Let S = Sana's age
Let M = Mona's age 
   S = M+18         (1)  (Sana is senior to Mona by 18 years)
   S+6 = 2(M+6)   (2)   (after 6 years Sana will be twice as old as Mona)

Substitute "M+18" for "S" from (1),  in (2):
   (M+18) + 6 = 2M + 12
     M + 24 = 2M + 12
            12 = M

M=12 —>   S=12+18 = 30

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Ans:  Mona is 12, Sana is 30
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Check:
         S+6 = 2(M+6)?
  Left side:       S+6 = 30+6 = 36 
  Right side:      2(M+6) = 2(12+6) = 2*18 = 36  (ok)