We define the following variables:
• x = age (in years) of the eldest,
,
• y = age (in years) of the second,
,
• z = age (in years) of the youngest.
From the statement, we know that:
0. the eldest is 7 years older than the second → , x = 7 + y,,
,
1. the second is 2 older than the youngest → ,y = 2 + z,,
,
2. the sum of the ages 12 years from now will be 56 → x + y + z + 12 = 56 → ,x + y + z = 56 - 12 = 44,.
We have the following system of equations:
i) Replacing the second equation in the first one, we have:
ii) Summing the ages of the three daughters, we have:
iii) Equalling the last equation with the third one, we have:
Replacing the value of z in the equation of x and y, we get:
Answer
The ages of the daughters are 20, 13 and 11.