Answer :
SOLUTION
Since it takes Kristin 10 hours to paint a fence
Hence the rate at which the job will be done per hour is is
[tex]\frac{1}{10}=0.1[/tex]Since it takes Deshawn 8 hours to paint a fence
Hence the rate at which the job will be done per hour is
[tex]\frac{1}{8}=0.125[/tex]Since Kristin do the job at a rate of 0.1 per hour and Deshawn does the job at a rate of 0.125 per hour then with the combined efforts the rate at which the job will be done is
[tex]0.1+0.125=0.225[/tex]Hence the job will be don at a rate of 0.225 per hour
The time it will take to complete the job will be
[tex]\frac{1}{0.225}=4.44[/tex]Therefore it will them approximately 4 hours to complete the job if they work together