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Jack's classmate, Mary,13, friends with him since their days at St. Gabriel's Primary School was overcome with emotion when she learned that he had passed away.

Are the underlined words correctly used?

Thanks in advance.
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Hi,

Jack's classmate, Mary,13, friends with him since their days at St. Gabriel's Primary School, was overcome with emotion when she learned that he had passed away.

Are the underlined words correctly used? Yes, but you need a comma as indicated.

There are a lot of sentence parts separated by commas here. I'd rewrite it as

Jack's classmate Mary,13 and friends with him since their days at St. Gabriel's Primary School, was overcome with emotion when she learned that he had passed away.

The comma in front of 'Mary' is often omitted.

Best wishes, Clive
Comments  
Thank you very much, Clive.