Can somebody help me with this. Will mark brainliest.

Which expression do you get when you eliminate the negative exponents of 4a^2 b^216a^-3 b

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?

According to the general equation for conditional probability if p(anb)=3/7 and p(b)=7/8 what is p(a i b)