jawab pake caranya pliss

1.15a-20b=2a=2b
   =15a+2a-20b+2b
   =17a-18b
2.6a+12ab+5ab
   =6a+17ab
3.6a-42b-3a-6b
  =6a-3a-42b-6b
  =3a-48b
4.maaf soalnya ga jelas
5.10a-15b+10a-6b
  =-21b