Amadeus and Benedict builds a toy car in 8 hours.
Benedict and Cooper builds a toy car in 6 hours.
Cooper and Amadeus builds a toy car in 2 hours.
How long does it take for Amadeus, Benedict and Cooper to build a toy car together?
Fraction of the toy car built by Amadeus and Benedict in 1 hour = ¹₈ 
Fraction of the toy car built by Benedict and Cooper in 1 hour = ¹₆ 
Fraction of the toy car built by Cooper and Amadeus in 1 hour = ¹₂ 

Total fraction of the toy car built by Amadeus and Benedict and Cooper in 1 hour
= (¹₈ + ¹₆ + ¹₂) ÷ 2
= (³₂₄ + ⁴₂₄ + ¹²₂₄) ÷ 2
= ¹⁹₂₄ ÷ 2
= ¹⁹₂₄ x ¹₂
= ¹⁹₄₈ 

Time taken for Amadeus, Benedict and Cooper to build a toy car together
= 1 ÷ ¹⁹₄₈
= 1 x ⁴⁸₁₉
= 2¹⁰₁₉ h

Answer(s): 2¹⁰₁₉ h or 2¹⁰₁₉ hours