At 10 a.m., Mrs Seah used two taps to fill up a tank. Tap A could fill the tank in 8 h. Tap B could fill the tank in 6 h. 1 hour after both taps were turned on, Tap B was faulty and stopped working. Mrs Seah accidentally opened Tap C which could drain a full tank completely in 2 h. Instead of being filled, the tank was emptied. How long did it take for the tank to be completely empty? Express your answer in mixed number.
Rate of Tap A per hour
= ¹₈ tank

Rate of Tap B per hour
= ¹₆ tank

Rate of Tap C per hour
= ¹₂ tank

Fraction of the tank filled per hour by Tap A and Tap B
= ¹₈ + ¹₆
= ⁶₂₄ + ⁸₂₄
= ¹⁴₂₄

Fraction of the tank drained per hour by Tap C when only Tap A is working
= ¹₂ - ¹₈
= ⁸₈ - ²₈
= ³₈

Time taken for the tank to be drained after first hour
= ¹⁴₂₄ ÷ ³₈
= ¹⁴₂₄ x ⁸₃
= 1⁵₉ h 

Total time taken for the tank to be empty
= 1⁵₉ + 1
= 2⁵₉ h

Answer(s): 2⁵₉ h