tolong jawab dengan cara

6.
5√20 + √80 - 2√45
= 5 √4 x 5 + √16 x 5 - 2√9 x 5
= 5.2√5 + 4√5 - 2.3√5
= 10√5 + 4√5 - 6√5
= 8√5

7.
128^8/7 : 16^3/4
= (2^7)^8/7 : (2^4)^3/4
= 2^8 : 2^3
= 2^5
= 32