I need some help plss asap

What percent of 18 is 24? and plz explain thx.

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”?

Solve 4 ln x=2ln25 a) x=5 b) x=25 c) x=625