We have, F = $\frac{9}{5}$ C + 32 but, 68 < F < 77 ∴ 68 < $\frac{9}{5}$ C + 32 < 77 Subtracting 32 from each side, we get - 32 < $\frac{9}{5}$ C + 77 - 32 ⇒ 36 < $\frac{9}{5}$ C < 45 Multiplying each side by 5/9, we get 36 × $\frac{5}{9}$ < C < 45 × $\frac{5}{9}$ ⇒ 20 < C < 25 ∴ Required temperature is between 20°C and 25°C.