Also, is x*5x equal to 6x or 5x^2?
If x^2*5x, does it equal 5x^2?
When multiplying variables, you need to add their exponents.
To answer your specific questions:
x2 * 5x = 5x3
x * 5x = 5x2
(In addition to John's response)
Algebraically: x = x1 , x · x = x1 · x1 = x1+1 = x2 ...... etc.
x^2*5x = x2 · 5 · x = 5 · x2 · x1 = 5 · x2+1 = 5x3