Question 248813
Farmer does 1/4 the job in 1 hour.
Both do 1/3 the job in 1 hr.
Let the son do  1/x the job in 1 hr.
.
1/4 + 1/x = 1/3
3x+12=4x multiply each side by 12x (LCM) to eliminate fractions.
x=12 hrs it takes the son to do the job alone.
.
Ed