She said the world is/was round. // She says she watches TV every day. // to teach somebody piano
1.
“She said the world is round.”
→Can I say “was” instead of “is”?

2.
“She says she watches TV every day.”
→Is the tense correct?

3.
“I still remember the man who taught me piano when I was a boy.”
→Is this sentence correct? Is there such a expression as “to teach somebody piano”?

Thanks!

Question

She said the world is/was round. // She says she watches TV every day. // to teach somebody piano
1.
“She said the world is round.”
→Can I say “was” instead of “is”?

2.
“She says she watches TV every day.”
→Is the tense correct?

3.
“I still remember the man who taught me piano when I was a boy.”
→Is this sentence correct? Is there such a expression as “to teach somebody piano”?

Thanks!

Answer

1. No 
2. Yes
3. No, these are the same questions asked a little differently.  Use this; I still remember the man who taught me to play the piano when I was a boy.  No:  ( She's going to teach him to play the piano. )

You may hear this informally "“to teach somebody piano” or "taught Billy to play piano" but i suggest you avoid it. To a native speaker it sounds coarse.