Question 18304
One approach is to find the hourly rate of Johnson and that of Maggie.

If t = number of hours, then, if t = 1 hour, Johnson can paint 1/4 of the fence in i hour and Maggie can paint 1/5 of the fence in 1 hour.
Together, they can paint (1/4 + 1/5) of the entire fence in 1 hour.

{{{1/4 + 1/5 = 9/20}}}

So, in 1 hour, they can paint 9/20 of the entire fence working together.

Therefore, it would take them 20/9 hours to paint the entire fence together.

20/9 hours = 2 2/9 hours.
2/9 hours = 13 1/3 minutes.
1/3 minute = 20 seconds.
20/9 hours = 2 hours 13 minutes 20 seconds.

T = 2 hours 13 minutes 20 seconds.