Answer:
knew
would have invited
Step-by-step explanation:
was is in the past tense, so we need to use the past tense for the verbs "know" and "invite".
Excellent. The past tense of know is "knew" and the past tense of invite is "invited".
Careful! For invited, we have to use "would have invited" because the statement makes it seem like they did not invite him to speak at their meeting (i.e. the "if we knew").
Hope this helps!