∵-2x^2m-1y与x^3y^n+3是同类项
∴2m-1=3;m=2
n+3=1;n=-2
∴-2(mn-3m^2)-[m^2-5(mn-m^2)+2mn]
=-2(-4-12)-[4-5(-4-4)-8]
=-32-(4+40-8)
=-32-36
=-68