$x^3 + y^3 = 35$ and $x + y = 5$, then the value of ($\frac{1}{x} + \frac{1}{y}$) is

x³ + y³ = 35

⇒ $(x + y) (x² - xy + y²) = 35

⇒ $5(x² - xy + y²) = 35

⇒ $x² - xy + y² = 7

⇒ $(x + y)² - 3xy = 7

⇒ $25 - 3xy = 7 (? x + y = 5)

⇒ $3xy = 18

⇒ $xy = 6

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