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?
In 7 weeks 5*7 = <<35=35>>35 goldfish die.
In 7 weeks, Martin purchases 3*7 = <<3*7=21>>21 goldfish.
In 7 weeks, Martin will have 18-35+21 = <<18-35+21=4>>4 goldfish.
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