A school ordered 0.5 of lumber for new nature path what is the weight of the lumber in pounds

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

What is the point-slope equation of a line with slope -5 that contains the point (6,3)

Ammonia molecules have three hydrogen atoms and one nitrogen atom.how many of each atom arein five molecules of ammonia