Conclusion right.

4. Some epicures are ungenerous;
All my uncles are generous.
My uncles are not epicures.

Univ. “persons”; m = generous; x = epicures; y = my uncles.

xm′1y1m′0xy′1 [Fig. II.

Conclusion wrong: right one is “Some epicures are not uncles of mine.”

5. Gold is heavy;
Nothing but gold will silence him.
Nothing light will silence him.

Univ. “things”; m = gold; x = heavy; y = able to silence him.

m1x′0m′y0x′y0 [Fig. I.

Conclusion right.

6. Some healthy people are fat;
No unhealthy people are strong.
Some fat people are not strong.