What is the formula for working out those questions that have 4 or more people that are diff ages and they?

Question

give you clues, like one is twice as old as the one that is 3 yrs older than the youhngest that is 1/2 as old as the oldest.
Not exactly that stuff but you know the word problems.

Also the ones with 2 trains leaving diff locations, diff speeds...

Answer 1

There is no formula. The purpose of these problems is for you to develop the habit of 'algebraic thinking', so that you translate words into formulas of your own.

For example, when I hear "Jill is twice as old as Jane was 3 years ago", I think "well, Jill's age is described in terms of Jane's age, so let x = Jane's age today. " Then I read through the problem step by step:

x = Jane's age today
x-3 = Jane's age 3 years ago
2(x-3) = Jill's age today

The hope is that if you get lots of practice doing these kinds of problems, this kind of thinking will eventually come naturally to you. (And will be a skill you can draw on for less frivolous applications in more advanced courses.)