Math gets on my nerves sometimes, help with this problem pls thx?

Okay this might be a easy problem, and maybe i just cant concentrate but i dont get this, its the last question to my math hw here we go....





A farmer can plow a field in d days. It takes his son 4 fewer days to the plow the same field.





a) Express in terms of d the part of the field that the farmer can plow in a day.





b) Express in terms of d the part of the field that the son can plow in a day





c) Express as a fraction in lowest terms the part of the field that the farmer and his son can plow in a day working together.





Those are the 3 questions (a,b,c), a brief explanation of how you arrived at the answer for each would be appreciated, anyways thanks for helping..

Math gets on my nerves sometimes, help with this problem pls thx?
a. The farmer can plow 1/d of the field in one day.





Think of it with numbers. If I can plow the field in 3 days, then I can plow 1/3 of it in a day.





b. The son can plow 1/(d-4) of the farm in a day. Same rationale.





c. Together, they can plow 1/d + 1/(d-4) of the field.


1/d +1/(d-4) = (d-4)/d(d-4) + d/d(d-4)


that's converting the fractions to the common denominator


(2d -4) / (d^2 -4d) is the final answer





your teacher may like 2(d-2) / d(d-4)
Reply:who gets homework on christmas eve?