SOLUTION: the sum of the present age of the father and his daughter is 42 years, 7 years. later, the father will be 3 times old than the daughter. the present age of the father is

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Question 909148: the sum of the present age of the father and his daughter is 42 years, 7 years. later, the father will be 3 times old than the daughter. the present age of the father is
Answer by clearblueskai(22) About Me  (Show Source):
You can put this solution on YOUR website!
let x =father's present age and y =daughter's present age
x%2By=42 - first equation
7 years later:
x+7 =father's age y+7=daughter's age
x%2B7=3%28y%2B7%29
x%2B7=3y%2B21%29 - second equation
use either elimination or substitution on the two equations
by substitution:
x=42-y
%2842-y%29%2B7-3y-21=0
4y=28
y=7
x%2B%287%29=42
x=35
Father's present age: 35