Answer :
12 because if you add it up 12 plus 5 is 17. And 17 plus 7 is 24. So 12 plus 17 plus 24 equals 53
Aaron=A
Bronwyn=B
Carl=C
A=B+5
B=B
C=A+7
C=B+12
A+B+C=53
(B+5)+B+(A+7)=53
(B+5)+B+((B+5)+7)=53
(B+5)+B+(B+12)=53
B+B+B+5+12=53
3B+17=53
-17 -17
_________
3B=36
(3B)÷3=36÷3
B=12
Bronwyn is 12 years old
Bronwyn=B
Carl=C
A=B+5
B=B
C=A+7
C=B+12
A+B+C=53
(B+5)+B+(A+7)=53
(B+5)+B+((B+5)+7)=53
(B+5)+B+(B+12)=53
B+B+B+5+12=53
3B+17=53
-17 -17
_________
3B=36
(3B)÷3=36÷3
B=12
Bronwyn is 12 years old