Martin has 18 goldfish. Each week 5 goldfish die. Martin purchases 3 new goldfish every week. How many goldfish will Martin have in 7 weeks?
Please answer the following question by reasoning step-by-step.
4
In 7 weeks 5 * 7 = 35 goldfish die.

In 7 weeks, Martin purchases 3 * 7 = 21 goldfish.

In 7 weeks, Martin will have 18 - 35 + 21 = 4 goldfish.

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The final answer: 4