Question 1104644
One job is wash five cars.


RATE of both people combined is {{{1/36+1/42}}} JOBS per MINUTES.

Lowest common denominator is {{{2*2*3*3*7}}}.


{{{(1/36)(7/7)+(1/42)(6/6)}}}

{{{(7+6)/252}}}

{{{13/252}}}

-

TIME:
{{{252/13}}}

{{{19.38*minutes}}}
or about 20 minutes.