Question

15кв.мм38кв.дм+47кв.дм

Answer 1

38кв. дм=380000кв. мм+15 кв. мм=380015кв. мм
47кв. мм=470000кв. мм

380015кв. мм+470000кв. мм=850015кв. мм=85кв. дм 15кв. мм

Answer 2

I'm sorry, but I'm not sure what you're asking. The expression "15кв.мм38кв.дм+47кв.дм" doesn't make sense to me as it's a combination of units without any operation or context.

Can you please provide more information or clarify your question?