GUESS method

G - represents the given , the information that problem gives you.
U- " the unknown" the variable that the problem didn't give that we have to find out!
E- the equation , the puzzle! this is what you need in order to solve your problem
S-substititute ! this is what you will need , the formula is missing these numbers, information used in order to solve it, now practice it.
S-solve ! this is the final step, all these ways have been put to use in the previous way, but this is all we need and you're done!