Answer:
10 yrs old
Explanation:
so Mavis is 20 years younger than aviva
it would take 20 years for her to catch up to Avivas age so we can take Avivas age as
A=m+20
a=avivas age
m=mavis's age
and it would take 3 times Avivas age for mavis to catch up so Mavis's age can be represented as
m=3a
lets substitute Avivas's age for "a"
m=3(m+20)
distribute
m=3m+60
bring "60" to the left and "m" to the right
-60=3m-m
-60=2m
divide both sides with 2
-30=m
we need to divide 30(since we cant have a negative age) by 3 to get mavis's age(since aviva is 3 times as old as mavis)
30/3=10
Mavis is 10 years old