What are the excluded values? m+5/mn+3m

values that are excluded from the domain of a rational expression are values that make the denominator 0, since if that's so, the rational will be undefined.  That happens when the denominator is zero out, let's do so

so, if ever m = 0, the denominator will become 0 and the rational becomes undefined, and whenever n = -3, the same will happen to the rational, thus those values are excluded.

b) well because you get well