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Tony = Tiana + 7.              (1)
(Tony+9) + (Tiana+9) = 53      (2)  ====>
Tony      + Tiana    = 53 - 9 - 9 = 35  ====>  Replace here Tony by (Tiana+7), based on  (1)  ====>  
(Tiana+7) + Tiana = 35  ====>
2*Tiana = 35-7 = 28  ====>  Tiana = 
 = 14.
Answer.  Tiana = 14 years old,   Tony = Tiana + 7 = 14+7 = 21.