a) =2√6+3√3·(8√3-8√3+4√2)
=2√6+3√3·4√2
=2√6+12√6=14√6
b) =50+2√5·(65√2-65√2+15√5)
=50+2√5·15√5
=50+30·5=50+150=200
c) =12√3+2·[20√2-(18√3-15√3+10√2]
=12√3+2·(20√2-3√3-10√2)
=12√3+40√2-6√3-20√2
=6√3+20√2
d) =90√3+2√3·[18√2-3√3·(8√6-6√6+15√3)]
=90√3+2√3·[18√2-3√3·(2√6+15√3)]
=90√3+2√3·(18√2-6√18+135)
=90√3+36√6-12√54+270√3
=360√3+36√6-12·3√3
=360√3+36√6-36√3
=324√3+36√6