Question about Eq numbering

[snvv]

Hello,

I would like to number some equations like this

Chapter.Section.eq_no
1.1.1
1.1.2a
1.1.2b
1.1.2c
1.1.3

or

Chapter.eq_no
1.1
1.2a
1.2b
1.2c
1.3

Is that possible?

Thank you
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