The standard form for writing a polynomial is to put the term with the highest degree first, then the term with the next highest degree, and so on.
So, x7 is the first highest degree
x5 is the second highest degree.
So, 5x7−x5+18x3−2x2+3x−2 is the standard form of the given polynomial 12x3−x5+5x7−2x2+6x3−2+3x