Help on all of them please thank you!

How do i put 3(x+7) in distributive property

Ab and bc are tangent to circle d. find x is ab = 3x + 8 and bc = 26. find x

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”?