Hi Wendy,

The secret to success in this type of problem is in the translation of information into a workable equation.

We always begin by choosing a variable to work with and saying what it represents, usually one of the numbers we are trying to find.

Let x = Petra's age

Next we use one of the relationships between Petra and her mother to conclude the mother's age.

2x + 12 = Petra's mother's age (her mom is 12 years more than twice as old as Petra)

Next we use the other relationship between Petra and her mother to set up an equation.

(sum of their ages) is 45
x + 2x + 12 = 45

Can you finish it from here?

Leeanne