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4. 3ã11 + 4ã11 Answer: 8ã11
7. 7ã2 - 2ã8 Answer: 1ã2 ??
8. ã48 + ã75 Answer: 9ã3
10. ã27/64 (Fractions) Answer 3ã3/8 ??
11. 10ã20 - 3ã80 Answer: 10ã5
12. ã6/49 Fractions) Answer: ã6/7 ??
13. 3ã2 * ã14 Answer:stays the same ??
15. ã30 * 2ã12 Answer: ã30 * 4ã3

If I got any of these wrong, can someone please tell me how to do them correctly?

I will assume your ã means 'square root'

4. 3ã11 + 4ã11 Answer: 8ã11 --- I recall 3+4 used to be 7, not 8

7. 7ã2 - 2ã8 Answer: 1ã2 ??

---- 7√2 - 2(2√2) = 3√2

9.(3ã10) Answer: 19 + 6ã10 --- how did you get that ????
---- 3√10 stays that way

11. 10ã20 - 3ã80 Answer: 10ã5 --- NO

10(√4)(√5) - 3(√16)(√5) = 20√5 - 12√5 = 8√5

13. 3ã2 * ã14 Answer:stays the same ?? --- no

----- 3√2 * √14 = 3√28 = 3(√4)(√7) = 6√7

14. ã6/50 Answer: 10ã3 --- not clear, is the 50 part of the square root ?
If so, then √(6/50) = √(3/25) = (√3)/5
If it is (√6)/50 then it stays that way

15. ã30 * 2ã12 Answer: ã30 * 4ã3 -- don't understand what you did

√30 * 2√12 = 2√360 = 2(√9)(√4)(√10) = 24√10