Can I add text or number fields to a multiple choice question?

Example: If someone requests tables, I need them to tell me how many they need. There are multiple options to choose from & some need a quantity and some do not.

Multiple Choice options:                 User provides # for specific options when checked

6 ft Conference table                     Qty needed: ­­____

6 ft Regular table                          Qty needed: ­­­____

6 ft Round table                           Qty needed: ___

Sound/Projector (no quantity needed)

If this can't be done, what are your suggestions to accomplish what I need to do?

In this case, I would recommend using individual number fields for the options that require quantity input.  For those that do not require quantity input, multiple choice fields would work. 

If you need to use a single field to collect the options, then show quantity fields based on what is selected in that field, that can be done using conditional logic:

https://www.jotform.com/help/316-How-to-Show-or-Hide-Fields-Base-on-User-s-Answer