What is the margin of error for 95% confidence for a sample size of 100 where p=0.15

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?

Rewrite 9 log, x2 in a form that does not use exponents. 9log, x = log, x

Sara has 2 2/3 cup taco meat. she needs 1/6 cup to make one taco. how many tacos can sara make with the taco meat she has?