I'm having problems with two rational expressions that need to be worked out. I really need a step by step example so that I can do it on the test I'll be having soon.

is it $\displaystyle \frac {8(y - 4)}{20-y} $ with y not equal to -3 for the domain?

$\displaystyle \frac {4y - 16}{5y+15} * \frac {2y + 6}{4-y}$

and

$\displaystyle \frac {x - 13}{x^3(3 - x)} * \frac {x(x - 3)}{5}$