<em><u>Answer</u></em>
5 hours
<em><u>Explanation</u></em>
The two working together can finish a job in

Also, working alone, one machine would take one hour longer than the other to complete the same job.
Let the slower machine working alone take x hours. Then the faster machine takes x-1 hours to complete the same task working alone.
Their combined rate in terms of x is

This should be equal to 20/9 hours.

Multiply through by;





Factor to get:


It is not feasible for the slower machine to complete the work alone in 4/9 hours if the two will finish in 20/9 hours.
Therefore the slower finish in 5 hours.
Some examples of environmental technology is recycling.
Answer: Why'd you'd Microwave your phone?
Explanation: Ok first don't do that, it can make it explode, and since you did that, it messed up something, you'll have to get it fixed or buy a new one
Hope this helps^^