Question 206130
Right now, "Ruth is twice as old as Pat."

let x = Pat's age
2x = Ruth's age

"In 4 years, Ruth will be three times as old as Pat was 3 years ago."

{{{2x+4}}} is Ruth's age in 4 years.  {{{x-3}}} is Pat's age 3 years ago.
Because Ruth will be three times as old, {{{2x+4 = 3(x-3)}}}

Solve.
{{{2x+4 = 3(x-3)}}}
{{{2x+4 = 3x-9}}}
Subtract {{{2x}}} and add {{{9}}} to both sides
{{{13 = x}}}
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Since x = Pat's age and 2x = Ruth's age, 
Pat is 13 now.
Ruth is 26 now.