4x²y³z/9 * 45y/8x^5z³

(5x²y⁴z/2x^5z³)

Step-by-step explanation:

That's a wacky looking multiplication! All you really need to do here is multiply straight across as you usually would; reducing terms and combining like terms where applicable.

(4x²y³z/9) • (45y/8x^5z³) =

(4•45•x²y⁴z/9•8x^5z³) = (<- - I reduce here)

(5•x²y⁴z/2x^5z³) =

(5x²y⁴z/2x^5z³)

You could put the "x" into the denominator as well and combine those terms, but I don't really see a good reason to do so.