x best represents mother's age.
x - 24 best represents Sarah's age.
Age of Sarah is 22
Explanation:
x best represents mother's age.
x - 24 best represents Sarah's age.
Sum of their ages is 68
That is
x + x -24 = 68
2x = 68 + 24
2x = 92
x = 46
Sarah's age = x -24 = 46 -24 = 22
x best represents mother's age.
x - 24 best represents Sarah's age.
Age of Sarah is 22