5. Jane can paint the office by herself in 7 hours. Working with an associate, she can paint the office in 3 hours. How long would it take her associate to do it working alone?

Step 1 ：Let's denote the work rate of Jane as $\frac{1}{7}$ office/hour, because she can paint the office by herself in 7 hours.

Step 2 ：When Jane and her associate work together, their combined work rate is $\frac{1}{3}$ office/hour, because they can paint the office together in 3 hours.

Step 3 ：We can find the work rate of the associate by subtracting Jane's work rate from their combined work rate.

Step 4 ：$\frac{1}{3}-\frac{1}{7}=0.19047619047619047$ office/hour, which is the work rate of the associate.

Step 5 ：We can find how long it would take the associate to paint the office alone by taking the reciprocal of the associate's work rate.

Step 6 ：$\frac{1}{0.19047619047619047}=5.25$ hours.

Step 7 ：Final Answer: It would take Jane's associate $\boxed{{\displaystyle 5.25}}$ hours to paint the office working alone.