Answer:
It would take Henry 3 hours to clean the office carpets if Mary were not there to help
Step-by-step explanation:
Assume that it takes Henry t hours to clean the carpets
∵ Henry takes 3 hours less than Mary to clean the carpets
∵ Henry takes t hours
- That means add 3 to t to find Mary time
∴ Mary takes t + 3 hours
∵ The rate of Henry is 
∵ The rate of Mary is 
∵ Working together, they can clean the carpets in 2 hours
- Add the two rates and equate the answer by 
(their rate together)
∴ 
Multiply the two denominators and multiply each numerator by the other denominator to add the two fractions of the left hand side
∵ 
∴ 
- Add the two fractions in the left hand side
∴ 
∴ 
Use the cross multiplication
∵ (t² + 3t)(1) = 2(2t + 3)
∴ t² + 3t = 4t + 6
- Subtract 4t from both sides
∴ t² - t = 6
- Subtract 6 from both sides
∴ t² - t - 6 = 0
- Factorize it into two factors
∴ (t - 3)(t + 2) = 0
Equate each factor by 0 to find t
∵ t - 3 = 0
- Add 3 to both sides
∴ t = 3
OR
∵ t + 2 = 0
- Subtract 2 from both sides
∴ t = -2 ⇒ reject this answer because there is no - ve time
∴ t = 3
∴ Henry would take 3 hours to clean the carpets alone
It would take Henry 3 hours to clean the office carpets if Mary were not there to help
