Let's simplify each expression step by step:

√12 √18 √216
= √(12 18 216) (Using the product property of square roots)
= √(3888)
= √(36 108)
= 6√108
= 6 √(36 3)
= 6 6√3
= 36√3

√75 √28 / √21
= √(75 28) / √21 (Using the product property of square roots)
= √2100 / √21
= √(100 * 21) / √21
= 10√21 / √21
= 10

√(4.3)^2
= √(4.3 * 4.3)
= √(18.49)
= 4.3

0.1√(-93)^2
= 0.1√93
= 0.1√(3 * 31)
= 0.1√(3)√(31)
= 0.1√93

Therefore, the simplified expressions are: