Set 1 

Hello, please check my results .
Ex 1 should be O(n), 
Ex 2 O(n^2)
Ex 3 O(n^3).

Thank you.
Best.
Cristina
Here you can shorten the runtime by using:
return true
This will exit out of the method and instantly return True. This way if you find two numbers that equal the sum, then you can exit the method then and not look at the rest of the combinations.