How to find the percentage of area under a normal curve?

What could explain what happened when the time was equal to 120 minutes

Jacob signs up to work for 2 1/2 hours at the school carnival. if each work shift is 3/4 hour, how many shifts will jacob work? (i just want to double check : |, for anybody that responds! : )

Solve each equation using the quadratic formula. find the exact solutions. 6n^2 + 4n - 11