Can someone explain this to me I already know the answer is 50 but how is it 50?

The number of nails of a given length is normally distributed with a mean length of 5.00 in, and a standard deviation of 0.03 in. find the number of nails in a bag of 120 that are less than 4.94 in. long.

Find the area of a parallelogram with base 15 yards and height 21 2/3

Prove that (x-2)is factor of p (x)=2x³-3x²-17x+30