I found the answer in an 8/25 post:
and(condition1,condition2)

"Arthur" wrote:

I'd like cell D5 to turn red if it is a negative value and cell C5 has a
value of 9. How do I set this up? I've tried entering a boolean formula such
as ...

+d5<0 #and# +c5=9

But Excel doesn't seem to recognize #and#.

I tried entering the second part of the formula as a second condition, but
that seems to be if you want the cell format to have multiple possible
outcomes.