Answer:
[tex]3m^3-7m^2n+3mn^2-n^3[/tex]
Step-by-step explanation:
[tex](5m^3 + 3mn^2) + (-7m^2n + mn^2 - n^3) - (mn^2 + 2m^3)\\Solving:\\5m^3 + 3mn^2 -7m^2n + mn^2 - n^3 - mn^2 - 2m^3\\Adding\,\,like\,\,terms\,\,\\5m^3 -2m^3+ 3mn^2 -mn^2+mn^2-7m^2n-n^3\\3m^3 +3mn^2-7m^2n-n^3\\Arranging\,\,in\,\,desecnding\,\,order\,\,in\,\,power\,\,of\,\,m\\3m^3-7m^2n+3mn^2-n^3[/tex]