Solution
Step 1
If k represents Kirsten's age
Kirsten's mum age = 3k - 2 years
Step 2
Sum of their ages
[tex]\begin{gathered} =\text{ k + 3k - 2} \\ \text{= 4k - 2} \\ =\text{ 2\lparen2k - 1\rparen} \end{gathered}[/tex]Final answer
2(2 k - 1)
4 k - 2
(3 k - 2) + k