Question 590816
12 to the square root of 3 times 5 to the square root of 15 
----------------
I'm going to assume you mean multiplication:
12*sqrt(3)*5*sqrt(15)
---
= 60*sqrt(45)
----
= 60*sqrt(9*5)
----
= 60*3*sqrt(5)
----
= 180*sqrt(5)
===============