[Grammar] How you doing expression usage

[cmarin.chile]

Good evening, I'd like to know the usages of the "how you doing expression", because today on a test I answered:
Richard told me that his dad wasn't doing very well.

Although I know that the usage of the expression is not too formal, I'd like to know if the answer I wrote down is correct so I can prove my English teacher I'm Right.

Thank you very much in Advance
Sincerelly yours

Cristian A. Marin
12th Grade Student
FCE and TOEFL preparing student

 

[Raymott]

Good evening, I'd like to know the usages of the "how you doing" expression, because today on a test I answered:
Richard told me that his dad wasn't doing very well.

Although I know that the usage of the expression is not too formal, I'd like to know if the answer I wrote down is correct so I can prove my English teacher I'm Right.

Thank you very much in Advance
Sincerelly yours

Cristian A. Marin
12th Grade Student
FCE and TOEFL preparing student

Yes, "How are you doing?" is correct colloquial English. Your sentence is good.
You also might hear "How you doing?", but it would be wrong to write it that way in a sentence, unless you're quoting.

 

[cmarin.chile]

Richard,
Thank you for your quick answer.
It'll be very helpful for me
Thank you very much