Common denominator and strategy 2/3 and 10/15

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 ratio of the change in y-values to the change in x-values for this function? a) 1: 13 b) 2: 5 c) 5: 2 d) 13: 1

The number of fish in a lake can be modeled by the exponential regression equation y=14.08 x 2.08^x where x represents the year