John gave his son mike 5z number of coins in addition to what he already has. mike then has (y + 10) times as many coins as he had originally. in terms of y and z, how many coins did mike have originally? explanation

Let X be the number of coin Mike has originally. 
Hi father gave him 5z got so he will have now: .
The sentence "mike then has (y + 10) times as many coins as he had originally"
can be written in math form like this:

We will solve the above equation for X like this:

Mike has originally  coins. 

I think it’s 6 1/4

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