Algebra and Equations Practice

If x - 1/x = 4, what is the value of x^3 - 1/x^3?

If x + 1/x = 3, what is the value of x^5 + 1/x^5?

In the following question, two equations I and II are given. Solve both equations and choose the correct relationship between x and y.
I. x^2 - 13x + 42 = 0
II. y^2 - 15y + 56 = 0

What is the value of a^3 + b^3 + c^3 - 3abc when a = 23, b = 24 and c = 25?

If x - 1/x = 3, what is the value of x^4 + 1/x^4?

If x - y = 4 and xy = 21, what is the value of x^3 - y^3?