Question

fathers age is three times the sum of ages of his two children.after 5 years his age will be twice the sum of ages of his two children.find the age in TWO VARIABLES

Answer 1

let the age of the father beY and set the age of the first child to a, and set the age of the secend child to b。So the sum of the age of the two children is a+b.
so，from the title we know :Y=3*(a+b);
and five years later,each of the age of the father,the first child and the second child is X+5,a+5 and b+5.So the sum of age of the two children is (a+5)+(b+5).So we can also get:
Y+5=2*((a+5)+(b+5));
Let's get the two equations together:
Y=3*(a+b);
Y+5=2*((a+5)+(b+5))=2*(a+b)+20. Y=2*(a+b)+15;
So,3*(a+b)=2*(a+b)+15;
We can get a+b=15,so Y=3*15=45.
So the answer is 45.