but is it ok to write to write words and calculation, after that words and calculation ( like kind of mixing words and calculations like answering ) instead of putting appendix at the last page ?
I would always do the appendix first, because you will need the results of the calculations to include in your report.
It is no problem doing it in that order – just make sure you head up the appendix pages as ‘appendix’ and the report pages as ‘report’, so that there is no risk of the marker being confused.