Question 909108
Ten years ago, father was 12 times as old as his son and ten years hence,he will be twice as old as his son.Find their present age.

x= father's present age
y= son's present age 

10 years ago:
{{{x-10 =father's age}}}
{{{y-10= son's age}}} 

10 years from now:
{{{x+10= father's age}}} 
{{{y+10 = son's age}}} 

Ten years ago, father was 12 times as old as his son:
{{{x-10=12(y-10)}}}
{{{x-12y+110=0}}}
Ten years hence, he will be twice as old as his son:
{{{x+10=2(y+10)}}}
{{{x-2y-10=0}}}

System of equations:
{{{x-12y+110=0}}}
{{{x-2y-10=0}}}

Eliminate one variable
{{{x-12y+110}}}+{{{(-x+2y+10)}}} = 
{{{-10y+120}}}
{{{y=12}}}
Plug in the value of y to any of the equations:
{{{x-2(12)-10=0}}}
{{{x-24-10=0}}}
{{{x=34}}}