Answer:
Therefore, Aroha is 17 yrs old and her brother is 14 yrs old.
Step-by-step explanation:
Let's represent Aroha's brother's Agee with the letter "b" yrs old.
If Aroha is 3yrs older than her brother, she's : (b+3) yrs old.
The sum of their ages is 31,
b+(b+3)=31
2b+3=31
Collect like terms,
2b=31-3
2b=28
Divide both sides by 2,
b=14
b+3=17
A cheerful teen hoping this helps,
stay techy, brilliant and positive!