



 
Hi Natakie. Try using algebra. You have to rewrite the question in terms of algebraic variables. Let p = Petra's age and m = Mother's age. Now interpret the question: "the sum of the ages of petra and her mother is 51."
"Her mother is 12 years more than twice as old as petra."
Since we know that m = 12 + 2p and p + m = 51, we can replace m in p + m = 51 becomes p + (12 + 2p) = 51. Can you solve this last equation and find Petra's age? Once you have that, you can easily determine the mother's age, too. Hope this helps,  


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