Answer:
8.47 Hours
Step-by-step explanation:
Allen can take 16 hours, while
Brianne can take 18 hours;
Therefore, in 1 hour Allen will complete a fraction of 1/16, while
in 1 hour Brianne will complete a fraction of 1/18
When working together, in 1 hour they will complete a fraction of (1/18+1/16)
= 17/144,
Therefore; to complete the whole project working together, they will take;
144/17 = 8.47 hours
