X is a normally distributed random variable with mean 97 and standard deviation 21. What is the probability that X is between 55 and 76?

True or false? many triangular shapes can be circumscribed about a given circle

What is the ratio of the length of an object in yards to the length of the same object in miles?

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?