Step-by-step explanation:
Mary's age = x
Billi's age = x+6
So, Mary age + Billi age = x + (x + 6)
Sum of their ages = 2x + 6
So, 2x + 6= 48
2x = 48 - 6
2x = 42
x = 42/2
Mary age = x = 21
And Billi age = x +6= 21 + 6 = 27
So Mary = 21
And Billi = 27
Lets check!
21 + 27 = 48
So therefore their ages add up to 48
So the answer is correct!
