The area of a rectangle is equal to length times width.
Mathematically, [tex]A_{rect}=l*w[/tex].
We can arbitrarily choose one expression for length and one for width; the result is the same.
Let's say that [tex]6x^3y[/tex] cm is the length, and [tex]5xy[/tex] cm is the width.
We simply write [tex](6x^3y)(5xy)=30x^4y^2 \ cm^2[/tex].
I am assuming you did not mean to write [tex]6x^{3y}[/tex] for the first dimension.
