Explain why 3(5x) is not equivalent to (3 x 5)(3 x x)

Answer 1

3(5x)
means : 3*5*x = 15x

Nothing to explain, just because of the "just the way it is" theorem

Answer 2

3(5x) = 15x
(3x)(5x) = 15x^2
only true if x=0 or x=1