Plz answer asap. explenation would be nice

Joel has twice as many CDs as Mariella has. Subtracting 7 from the number of CDs Joel has and dividing by 3 equals the number of CDs Blake has. If blake has 25 CDs, how many CDs does Mariella have?

Blake has 25 CDs. By doing the inverse operations, we can figure out how many CDs Joel has. 25*3 is equal to 75, plus 7 equals 82. Dived by two to get the amount of CDs Mariella has, 41 CDs.

Guest's answer and explanation are correct; my approach would be:

Let J represent the number of CDs that Joel has.

Let M represent the number of CDs that Mariella has.

Let B represent the number of CDs that Blake has.

Since Joel has twice as many CD as Mariella has:  

     J  =  2M                  (equation 1)

Since subtracting 7 from the number of CDs Joel has and dividing by 3 equals the number of CDs Blake has:

     (J - 7) / 3  =  B         (equation 2)

Since Blake has 25 CDs, substitute 25 for B into equation (2):

     (J - 7) / 3  =  25

     --->   Multiply both sides of this equation by 3:

     J - 7  =  75

     --->   Add 7 to both sides of this equation:

     J  =  82

So, Joel has 82 CDs.

Now, substitute this value into equation 1:

     82  =  2M

So, Mariella has 41 CDs.

Let the number that Mariella  has = x

Let the number that Joel has = 2x

And Blake has :   [2x - 7] / 3  =  25

Multiply both sides by 3

2x - 7 = 75     add 7 to both sides

2x = 82          divide by 2

x = 41  = Mariella's

2x = Joel's  = 82