-5(5a-2b+c)-2[3a-5(a-2b-3c)]
=-25a+10b-5c-2[3a-5a+10b+15c]
=-25a+10b-5c-2[-2a+10b+15c]
=-25a+10b-5c+4a-20b-30c
=-21a-10b-35c