Question 537277
x/f+x/s=1
f=8
s=12
every hour the farmer does 1/8 of the job
We know that together they can do it in less than 8 hours since the farmer can do it alone in 8 hours


x/8+x/12=1
x=24/5 or 4.8 hours working together.

24/5/8+24/5/12=1
3/5+2/5=1
5/5=1
or 
4.8/8+4.8/12=1
.6+.4=1
1=1
ok