Question

Незнайка сочинял небылицы по средам, субботам и воскресеньям, а в остальные дни говорил правду. В какие дни недели он может сказать: "Я лгал вчера" "Я буду лгать завтра" "Я лгал вчера и буду лгать завтра"

Answer 1

в среду т.к. в этот день он мог лгать. Т.е. он мог соврать что лгал вчера(хотя вчера был вторник и он говорил правду) и солгать что будет врать завтра(хотя и завтра, в четверг, он будет говорить правду). 

Answer 2

Я лгал вчера"- четверг
"Я буду лгать завтра"- вторник, пятница
"Я лгал вчера и буду лгать завтра"- ни в какой

Answer 3

Nonsense Days and Truth-Telling Days

Nonsense days and truth-telling days can be determined for the character Nезнайка based on the given conditions.

Nезнайка's Nonsense Days: Nезнайка's nonsense days are when he tells lies. According to the given conditions, Nезнайка tells lies on Wednesdays, Saturdays, and Sundays.

Nезнайка's Truth-Telling Days: Nезнайка's truth-telling days are when he tells the truth. Based on the given conditions, Nезнайка tells the truth on Mondays, Tuesdays, Thursdays, and Fridays.

Statements Nезнайка Can Make

1. "Я лгал вчера" (I lied yesterday): - Nезнайка can say "I lied yesterday" on a truth-telling day, as it would be a true statement if it is not a Wednesday, Saturday, or Sunday.

2. "Я буду лгать завтра" (I will lie tomorrow): - Nезнайка can say "I will lie tomorrow" on a truth-telling day, as it would be a true statement if it is not a Wednesday, Saturday, or Sunday.

3. "Я лгал вчера и буду лгать завтра" (I lied yesterday and will lie tomorrow): - Nезнайка can say "I lied yesterday and will lie tomorrow" on a nonsense day, as it would be a true statement if it is a Wednesday, Saturday, or Sunday.

Therefore, Nезнайка can make the first two statements on his truth-telling days, and he can make the third statement on his nonsense days.

Conclusion

Nезнайка can say "I lied yesterday" and "I will lie tomorrow" on his truth-telling days, and he can say "I lied yesterday and will lie tomorrow" on his nonsense days, based on the given conditions.