Question 815902
Let h = the time in hours for the new computer to do THE ONE JOB.
Theses numbers or expressions represent the three different work rates:
Old, 1/(h+3)
New, 1/h
Together, 1/5
Watch carefully that those rates are in jobs per hour.


Old computer's rate plus New computer's rate is the rate for both computers working together.


{{{highlight(1/(h+3)+1/h=1/5)}}}
If you solve for h, then you can also determine or compute the old computer's rate.