Are you saying (a^2 y^-18)/(a^2 y^-15) = 18/15 ? if so, then y^-3 = 6/5 y^3 = 5/6 y = (5/6)^(1/3) sub back into a^2 y^-15 = 15 a^2 (5/6)^-5 = 15 a^2 (6/5)^5 = 15 a^2 = 15(5^5)/(6^5) a = ± √(15(5^5)/(6^5))
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