Question 926486
This is a common word problem. You are told Carlo can do the job in 6 days. So Carlo can do {{{1/6}}} of the job in a day.

You do not know what Jordan can do, but let's say that Jordan can do the job in X days. So Jordan can do {{{1/X}}} in a day.

Together, the can do the job in 4 days. So they can do {{{1/4}}} of the job in a day .

{{{(1/6) + (1/X) = 1/4}}}
{{{ 1/X = (1/4) - (1/6)}}}
{{{1/X = 6/24 - 4/24}}}
{{{1/X = 2/24}}}
{{{1/X = 1/12}}}
{{{X=12}}}
Jordan will take 12 days working alone