Split Columns Within a List

Hello,

I'm currently working on the questions page for a math textbook and have run into an impasse.

I'm trying to place a numbered list (which is a 3-split column) within another numbered list. However, I don't know how to do this. I'm attaching a screenshot.

Please note Questions 1-6. I am aiming to have the alphabetically numbered list sit on the same line as the numbered list. Both use paragraph styles which contain a list element, and not manual formatting with tabs, spaces, etc.

I appreciate any help.

Thank you.