AverageIfs, Max and Min

Can someone please tell me what is wrong with the formulas in Q15 an Q17 on the attached spreadsheet.

I have a few other questions that are asked on the sheet attached.

There are no numbers in A21:A61 which are greater than B10.

you can rewrite this formula

=AVERAGEIFS($B$21:$B$61,$A$21:$A$61,">="&$B$3,$A$21:$A$61,"<="&$D$3,$A$21:$A$61,">="&$D$47,$A$21:$A$61,"<="&$B$8,$A$21:$A$61,">="&$D$8,$A$21:$A$61,"<="&$B$9,$A$21:$A$61,">="&$B$10,$A$21:$A$61,"<="&$D$10)

In this simple way

=AVERAGEIFS($B$21:$B$61,$A$21:$A$61,">="& MAX($B$3,$D$47,$D$8,$B$10),$A$21:$A$61,"<="&MIN($D$3,$B$8,$B$9,$D$10))

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