Each of Alice and Beatrice has their birthday on the same day. In 8 years' time, Alice will be twice as old as Beatrice. Ten years ago, the sum of their ages was 21. How old is Alice now?

Answer 1

present time:
Alice --- a
Beatrice --- b

10 years ago:
a-10 + b-10 = 21
a+b = 41 **

in 8 year's time:
a+8 = 2(b+8)
a+8 = 2b + 16
a - 2b = 8 ***

subtract *** from **
3b = 33
b = 11 , then a = 30

State your conclusions

Answer 2

so put the words into math.
a+8 = 2(b+8)
a-10 + b-10 = 21
so, a=30