Question 365291
If you add Harry's rate of working and Judy's rate of working,
you get their rate working together
given:
Harry's rate:
(1 house)/(6 days) = {{{1/6}}}
Judy's rate:
(1 house)/(x days) = {{{1/x}}}
{{{1/6 + 1/x = (x + 6)/(6x)}}}
This says that, working together, they can paint {{{x + 6}}}
houses in {{{6x}}} days
Or, what is the same thing, {{{(x + 6)/(6x)}}} houses in 1 day
So, they will paint {{{(2x + 12)/(6x) = (x + 6)/(3x)}}} houses in 2 days
{{{F(x) = (x + 6)/(3x)}}}