How do you calculate percentage?

say we have 374$ and 7% of this amount will make 26.18. so when we add 374 and 26.18 we come up with 400.18.



now somebody says to you 400.18$ includes 7%. how do you calculate original 374$ knowing only 400.18% and 7%??How do you calculate percentage?
You know that $400.18 is the cost of Item X including a 7% (lets say tax).



Putting this into an equation you get:



400.18 = 1.07X

Therefore X =

400.18/1.07 = 374