Answer:
24
Explanation:
To find how old Mrs. Roberts was when her son was born, we first need to know both of their ages. I'm going to give Mrs. Roberts the variable m and her son the variable s.
Let's turn the two sentences about their ages into equations:
m=Mrs. Roberts and 3s= three times as old as her son
m=3s
m+s is the sum of their ages
m+s=48
Now substitute the first equation into the second one:
m+s=48
(3s)+s=48
4s=48
s=12
The son is 12 years old. Now substitute s into one of the equations to solve for the mother's age:
m=3s
m=3(12)
m=36
Mrs. Roberts is 36. Since they are asking how old she was when her son was born, we will subtract her son's age from her age, since she would be 12 years younger:
36−12=24
Mrs. Roberts was 24 when her son was born.
credit to CountryGirl on Socratic Q&A