Rosamaria is setting up a -gallon saltwater fish tank it content of  a salt is . 

Rosamaria has water that has salt and water that has

Find gallons of water with salt content.

Find gallon of water to be added with salt content.

Let is number of milliliters of water to be added.

Make a table:

Content of salt	Amount of gallon	\ Total amount of gallon \

Observe the table:

Amount of salt    plus   Amount of salt    equals    Total amount salt.

.

Solve the equation.

         (Original equation) 

                      (Simplify)

   (Subtract from each side)

                                               (Apply additive inverse property : )

                                     (Divide each side by )

                                                     (Cancel common terms)

gallons of water is to be added with salt content.

gallons of water is to be added with salt content.