John is twice as old as fred. four years ago john was 6 times as old. how old is john?

These two equations from the question!
Fred + 6 = John , John + 4 = 2Fred

Now we’re going to use the 2nd equation:
John + 4 = 2Fred
(Fred + 6) + 4 = 2Fred
Fred + 10 = 2Fred
10 = Fred

Now we’re re going to use first equation:
Fred + 6 = John
10 + 6 = John

So, John is 16 years old!

Re-do the question and enter the picture