Devid has an algorithm X for a problem with time complexity X that is polynominal over input size.
Jack has an algorithm Y for another problem with time complexity Y that is exponential over the input size,
Michel has an alogrithm Z for another problem with time complexity Z that is double exponential over the input size.
which is correct
1.theta(X)=theta(y)
2.theta(X)=theta(Z)
3.theta(Y)=theta(Z)
4.O(Z)=X