Describe and correct the error in simplifying the expression

Use the normal approximation to the binomial distribution to answer this question. fifteen percent of all students at a large university are absent on mondays. if a random sample of 12 names is called on a monday, what is the probability that four students are absent?

In simplified exponential notation, the expression a^2•a^-3•a 1/a 0

What is the value of x in the following equation. -x ^3/2 = -27