How do i answer this??

You can see that the common factor is 3 so 3×2 =6 so thats where root 2 comes from. You multiply and the radical goes away hence the answer is Combine like factors such that 18 × 8 =144 and the square root of 144 is 12 hence the answer is 12

Iam not sure , but probably 750 or 7.5