+678 The following is known about the respective ages of the three sisters Alina, Melina and Selina:
(1) Alina is twice as old as Selina.
(2) Alina and Melina are 20 years old together.
(3) Selina is two years younger than Melina.
(a) Find out the age of each of the three sisters.
(b) Three years ago, the mother of the three sisters was twice as old as all the sisters. In how many years will the mother be twice as old as Alina
will be then?
My answer to this task:
If you try to find out the age all the time, then you have to make possible correct attempts, this came out:
a) Alina is 12 years old (\(6*2\)), Selina is 6 years old (\(12:2 \)) and Melina is 8 years old (\(20-12\)).
b) The mother is twice as old as all the sisters (3 years ago). All sisters together add up to (\(12+6+8=\)) 26 years, and then the mother is (\(26*2= \)) 52 years. But since it was 3 years ago, the mother is now (\(52+3=\)) 55 years old and Alina (\(12+3= \)) 15 years old (Please correct me now if something is wrong or I have misunderstood the task!). Let's make a chart...:
| + yo. | Mother | Alina |
| 0 yo. | 55 yo. | 15 yo. |
| 20 yo. | 75 yo. | 35 yo. |
| 5 yo. | 80 yo. | 40 yo. |
Now it turns out that Alina will be twice as old in (\(20+5=\)) 25 years as her mother will also be in (\(20+5=\)) 25 years. (Mother: 80 yo. and Alina: 40 yo.)
... yo. \(=\) years old ...
Straight's answer
