Jennifer is building tanks to hold her goldfish. She built 3 tanks that will hold 15 fish each, heated, and filled them. She plans to build the rest of the tanks equipped with heaters, and they will hold 10 fish each. If she needs to build enough tanks to house a total of 75 fish, how many more will she need to build?
With the tanks already built it has room for 3 tanks * 15 fish/tank = <<3*15=45>>45 fish.
The total of fish that still lack space is 75 fish - 45 fish = <<75-45=30>>30 fish.
This means Jennifer needs 30 fish / 10 fish/tank = <<30/10=3>>3 tanks of 10 fish.
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