In order to find out which equation can be used to solve the given problem, let us analyze the problem first.
Let x be the age of Sara.
So ralph = 3x
In six years (+6) Ralph = 2x
Now, find the age.
So, the correct equation would be this: 3x+6=2(x+6)
The answer is the third option.
Hope this is the answer that you are looking for.