A company manufactures two types of devices: basic models and advanced models. Each basic model requires 4 hours of assembly, and each advanced model requires 7 hours of assembly. A total of 65 assembly hours were spent on a batch of these devices. The relationship between , the number of basic models, and , the number of advanced models, is given by the equation . If 7 advanced models were assembled, how many basic models were assembled?
3
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6
