Add and Subtract Radicals

Simplify 
-10√7 + 12√7

• -2
• -2√7
• 2√7
• Already simplified 

Simplify 
3√8 + 3√2

• 9√2
• 6√10
• 5√2
• Already simplified 

Simplify 
3√5 + √20 - √45

• 3√-20
• 2√-20
• 3√5
• 2√5

Simplify

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Simplify $3\sqrt{45}\ +\sqrt{5}$

• Cannot be simplified.

Simplify $6\sqrt{75a^3}-3a\sqrt{3a}$