1 table seats 8 chairs. Each extra table adds 6 more chairs (the joined sides overlap).<br>For 4 tables: 8 + (3 x 6) = 26 chairs.<br>For 15 tables: 8 + (14 x 6) = 92 chairs.<br><br>Final Answer: 4 tables = 26 chairs, 15 tables = 92 chairs